[larsdangly]

This is a really good question. There is a passage in the rules on Attribute Enhancing Items (a greater magic item) that indicates total DX bonus from all magical sources can't exceed 5 (though, strictly speaking, it only clearly states that the total of an Attribute Enhancing enchantment + another source can't exceed 5, so no limit is placed on the total of 2 or more other sources). You can find another passage that says the highest bonus applies rather than adding, though I can't recall the context. Finally, it says you cant use attribute enhancers to raise final adjusted DX for an action above 14 (though this includes penalties from armor and perhaps other things). Frankly, it is all pretty confusing, and says nothing about adding fine weapon and magic enhancements. So, you will get answers that provide opinions, but they won't be definitive rulings.

Personally, I think magic and fine weapon bonuses should stack.

Edit: the magic item rules can 'break' a game if you permit one side to have very high bonus items and other side doesn't. Typically, that means Monty Haul distribution to players while NPCs and monsters go without. If you play TFT this way, PCs can be nearly invincible. But if this happens, the GM is to blame. The RAW governing the creation, prices and market availability of fine and magic weapons are actually pretty limiting. In my campaign, I don't hand out much in the way of magic items as treasure, little is available for direct purchase, and players often undertake their own enchantments to get the things they want. No one is going to bust open the rule of 5 very soon in a game like that. But, if you like games where PCs are extremely geared up, you can do it. And if that's fun for everyone, go for it!