>craft silk into pair of plain white trousers
>You lay the fine fabric out and begin to sew.
....after a while...
>You don't have the skill to make anything from that.
Err.. only two things that happened to me before .. While crafting, if someone steals the item you're crafting from you (heh, which's not a very nice action) or someone gives/plants a thing with the same keyword you used to you, such message appears. Other than that, it's possibly a bug.
Also if you used some command on some -other- piece of silk in your inventory, just before using the craft command, then the craft command might try to target the wrong piece of silk. Or if you have more than one kind of silk item in your inventory, you have to make sure the one you want to use is on the top of your inventory list.
So..
inv
A pair of white silk gloves
A length of white silk
will give you an error when you try to craft the length, because the command will target the gloves.
Try
craft length into pair of white silk trousers
instead.
Unless of course you have a length of linen on the top of your inventory list..basically though, just keep track of what's in your inventory, and what order it's in, and try to put -only- the material you're trying to craft in your inventory.