Ah! Thanks but I have just noticed something..
I have been having trouble with resizing some windows lately, mainly opera and my email client but others as well.
Opera can't adjust the width for instance and to adjust the height you can only drag up from the top, not the bottom.
Anyway with breezy auto sizing windows when automatically grouping Browser windows this has become more annoying and I had the idea it might be WindowBlinds causing it. So I disabled WindowBlinds and not only do the windows resize as normal but the Tabs on groupy now go red when I select them!
So it looks like you have a bug with the interaction with WindowBlinds.
To be honest I have found WindowBlinds fairly buggy in general so I will stop using it.