When I try to further craft a composite bow (req 16) and a heavy +3 mace the game crashes,, I don't even have an option to try again with a 'clean' masterwork weapon, it doesn't show up in my menu. Sometimes I can craft with other armour and arms, Ioio's crossbow did crash but I can now, the above sticks though, but it seems random... I have a bunch of other niggles, no Verbobon for example (I have the quest triggered by Smythe, but no option to get there, it's just not on my map. So I think my whole game has gone bad.
A non epic magic weapon can't have an enchantment greater than +10. If u try to add more enchantments the game crashes. Also if the Name of the crafted weapon or armor becomes to long, the game will crash as well. U can read a bit about crafting here: http://www.co8.org/forum/showthread.php?t=8742&highlight=silver+sword+chaos
Also make sure the new name of the crafted item does not exceed the length of the box it is shown in during crafting.
I have enough XP and it worked fine for the rest of my weapons.. they all exceed the size of the box.
If every time you craft an item the name is longer than the box it shows in, you my friend have been very very lucky that it did not crash on you when you clicked create item. Maybe you should buy a lotto ticket.
It may be that your game has too many snafus. You might want to try to reactivate the modual and start a new game.