No-no...I was just making sure that's what you were using. If you can get ahold of a small piece of pipe to extend the length of the allen-wrench that might give you the leverage you need to break it free...or even putting a crescent wrence on the end to extend the length or locking a pair of vise-grips on the end of the allen-wrench.
Don't mean to insult, but I've done it wrong myself: you are turning it the correct way, yes?
You could also try some solvent on the threads...there is likely loctite in there, and even iso alcohol will soften the loctite. WD-40 won't touch the loctite...far too weak a solvent. Acetone works really great but you have to be careful not to get it on anything alse.
If the extender doesn't do the trick, and you have allowed some time for the WD-40 or penetrating oil to work its way in (overnight even), a last resort is, depending on how accessible the cap screws are and the hub, is to take one of those little hand-held butane torches and heat up the hub. Avoid heating the cap-screw. This will expand the aluminum hub enough usually to allow the fastener to break free. You can see why this is a last resort, and you'd have to use your best judgement as far as whether or not you've got enough working room to avoid damaging surrounding components, etc.