gaining muscle (an excuse?)

My friends are always making excuses for my lack of weight loss by saying I'm gaining muscle mass.  My question is:  How much muscle mass can you really gain (as reflected in pounds on the scale)?  I mean, how far can you really take that excuse?

BTW, it's true that I must be gaining some muscle because I lost another 3/4 of an inch around my hips without losing a single pound.  

I am having this same type of trend...haven't lost much more than a pound in over a month now but I continue to shrink.  I am doing the P90 series and noticing a lot of muscle gain.  How much, I do not know, so I can't answer your question. But I really do think some people build muscle easier than others - maybe you are one of those people. I think I am. 

I am so glad I measured myself at the beginning of this, otherwise I would be extremely frustrated with the loss of pounds!  Good luck!