The most commonly used verse to support the doctrine of Sola Scriptura is 2 Timothy 3:15-17:
And that from a child thou hast known the holy scriptures, which are able to make thee wise unto salvation through faith which is in Christ Jesus. All scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness: That the man of God may be perfect, thoroughly furnished unto all good works
The Reformers believed the Scriptures was the only tool we have to make the man of God perfect and the Scriptures are all Christians need for their guiding authority. But there are two initial problems with this assumption. In Ephesians 4 we are told that there are other things that God has given to perfect us:
And he gave some, apostles; and some, prophets; and some, evangelists; and some, pastors and teachers; for the perfecting of the saints, for the work of the ministry, for the edifying of the body of Christ: Till we all come in the unity of the faith, and of the knowledge of the Son of God, unto a perfect man, unto the measure of the stature of the fulness of Christ
Scripture is never even mentioned in this verse and these roles are not mentioned in previous verse from 2 Timothy. Both verses provide different ways to attain perfection and neither cancels each other out. The assumption that only Scripture can aid in perfection can not be honestly held to. It would also appear to be at odds with the common Christian life to put forth the idea that Scripture alone perfects. What of repentance and prayer? Surely the Scriptures are an aid as they point us to prayer and repentance, but the Scriptures do no perfect us alone.
The second issue is the context of the phrase, "holy scriptures" in 2 Timothy 3:15. There may have been some epistles and Gospel narratives that were considered scripture at the time Paul penned this epistle, though unlikely, but Paul here is referring to the Scriptures Timothy knew as a child. This verse can only be referring to the Old Testament, not the New, and nobody puts forth the notion that Old Testament alone can perfect a man.
Scripture itself points to Tradition as the source of Truth, not back at Scripture itself. When looking for the "pillar and ground of truth", in 1 Timothy 3:15 Paul says it is to be found in the Church, "I write so that you may know how you ought to conduct yourself in the house of God, which is the church of the living God, the pillar and ground of the truth."
Paul when writing both 2 Thessalonians 2:15 and 1 Corinthians 11:2 commands the brethren to "stand fast and hold to the traditions" and "keep the traditions" the Apostles have handed down. In 2 Thessalonians he uses the phrase, "whether by word or our epistle". Some parts of Apostolic doctrine were written down and some were not, but Paul requires that we are to hold fast to both.
Later Paul will instruct Timothy that ,"The things which you have heard from me in the presence of many witnesses, entrust these to faithful men who will be able to teach others also. (2 Timothy 2:2)" This verse doesn't mention traditions being written down. Paul tells Timothy something and Timothy is expected to tell others the same, and they also will go on to teach others. We believe this tradition continues in the Orthodox Church today.
But isn't tradition a bad thing? To be sure, there are plenty of verses that speak of tradition in a negative light. Christ often lays into the Pharisees for teaching and following the traditions of men, such as, "For laying aside the commandment of God, you hold the tradition of men... making the word of God of no effect through your tradition which you have handed down. (Mark 7:8-13)"
Though Christ has nothing good to say about the tradition of men, we should not conclude that all tradition is a negative thing, but from the verses mentioned above, tradition is also a good thing, and even according to Paul necessary. Traditions of men like those of the Pharisees should not be confused with the Traditions of God that the Apostles command us to obey. Jesus and the Apostles seem to be able to tell the difference.
The National Association of Evangelicals did something interesting when the made the NIV translation. The Greek word used for tradition is paradosis. The same word is used in both the positive and negative perspectives mentioned above. The word for teaching is didaktos. In the verses that speak of tradition in a negative light the word paradosis was trasnlated as tradition, but in the positive perspective paradosis was translated as teaching. Rather than just translating, they went a step further, and interpreted the word to their own bias. Joe Heschmeyer, in his article, The NIV on Tradition and Teachings, sums up the situation:
The trouble is that the Christian Reformed Church and the National Association of Evangelicals have a long-standing tradition that tradition is bad, and were willing to warp Scripture to accord with their tradition. As Christ said in Matthew 15:6, "Thus you nullify the word of God for the sake of your tradition."
Besides all this, if Sola Scriptura was a doctrine taught and believed by the early church, they would have had a very hard time living it out. The bible as we know it today did not fall out of the sky. It was a long 300 year period before we had a canon close to what we have now. There was no divine table of contents. By the 4th century we have three known bibles or codexes, but they don't agree. They have different books in them! Most churches wouldn't have been able to afford all the books we call the bible. The early church had to rely on faithful men who had been entrusted the teaching from other faithful men all the way back to the Apostles.