Heard but never read up, very nice.Ever heard of the King of Smack?
See? Common sense dictates that you shouldn't be able to attack with a claw in the same hand you're holding a weapon, as do plenty of creatures' description. But there aren't any hard rule on the subject to fend off rules lawyers!
... snippage...
If it's just about the part where attacking with a manufactured weapon and a clawed appendage wielding that weapon...
I actually can't find anything anywhere explicitly saying the claw attack can't be used in general. The Lycanthrope template does say in it that "A hybrid may attack with a weapon and a bite, or may attack with its natural weapons." but that only refers to the hybrid lycanthrope form and not every creature ever. http://www.giantitp.com/forums/showthread.php?t=207742, http://www.minmaxboards.com/index.php?topic=482.0, and other places do refer to not being able to use the clawed limb for a claw attack while wielding a weapon in the claw but I can't find the exact rules quote.
Well, I can find stuff saying you can't make a secondary claw attack after you've used the limb for a primary attack.
There's also a bit from the FAQ saying that a Lizardfolk can't make a claw attack along with, say, an attack with a longsword in the clawed hand.
What happens when creatures use their natural
weapons as secondary attacks along with a manufactured
weapon? For example, lizardfolk have two claws that also
serve as hands. What happens when they wield a onehanded
weapon in one hand and nothing in the other? Do
they lose both claw attacks in exchange for their attacks
with the weapon?
Wielding a manufactured weapon doesn’t prevent a
creature from using all its natural weaponry, provided that the
creature is using the full attack action and the additional natural
weapons are free.
The example lizardfolk can’t make a claw attack with the
“hand” that holds its weapon, although it does get to attack
with the weapon itself. But, if it’s using the full attack action, it
can use its other claw as a natural secondary attack (–5 to
attack rolls, half Strength bonus), and can also bite as a natural
secondary attack. In effect, the lizardfolk is using its normal
full attack routine with the manufactured weapon attack
substituted for one claw attack.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.