There were a couple skill related bugs like this, both fixed in the patch. The one you are probably thinking of was that if you learnt a skill to a certain level, and then later learned it from a book at a lower level, the maximum skill level would be reduced (unless you had invested enough skill points to get it above the book level). The other similar skill problem was that some of the skills offered by the BF traders would not actually be learned, though they would take your money.
I don't think anyone has compiled a list of known issues.
