Been using Parallels for a long time - well before the intial release when it was in beta. I have a MBP, 2GB Ram - fully updated as of today. I've had a very irritating problem, not sure if it is Parallels or Mac/OSX but it only happens when use a VM with parallels. In System Preferences, Keyboard and Mouse, Trackpad I use the setting "Place two fingers on trackpad and click button for secondary click". In fact I will not use my MBP without that setting. I believe it is the best right-click ever. So anyway, it works well in a Windows VM. Sometimes when I exit Parallels - this feature stops working in OSX. IF I open System Preferences, Keyboard and Mouse, Trackpad the option is still selected, but placing two fingers on the trackpad and clicking does nothing. If I uncheck and then recheck this option - it works again. Any advice? It sure is irritating.
I use this with parallels also and have never seen it stop working as you describe. If no others respond indicating they have a similar experience, then it is likely that some other piece of software is responsible.
Once I set this, it has worked perfectly. Before I set it though it didn't seem to work..... ;-) Funny that.