NSInvocation problem

FROM : alex
DATE : Wed Nov 24 22:08:25 2004

I have a small problem with NSInvocation, im setting an invocation up
like this:

// setWidth: is a method defined by self.

NSMethodSignature*    sig = [LayoutControl
instanceMethodSignatureForSelector: @selector(setWidth:)];
NSInvocation*        incovation = [NSInvocation
invocationWithMethodSignature:sig];
[invocation setSelector: @selector(setWidth:)];
[invocation setTarget:self];

whenever i try and invoke it, i get this error message:

2004-11-24 16:04:04.970 Cocode[4943] *** -[NSInvocation copyWithZone:]:
selector not recognized

Whats going n here and how can i fix it? Can my invoced method have non
"NS" types?

thanks
Alex