Re: How to free up RAM space?
I'm afraid you don't want to do that. It controls your panel (or at least a good deal of things you use the panel for). You'll see that if you kill the associated process wnck-applet (you can do that from the 'system monitor'), some things get unusable in the panel, and if you restore them, the wnck-applet process will start again.
What is that wnck-applet for? Can I disable it?
Your best bet (as for my knowledge so far) is to see if some of the tricks mentioned in my previous post fix your problem.
Not a 'fix', but if you don't get it fixed, and you're still interested in running an older version of ubuntu (again what is it?), you can use a different desktop environment. I use mainly lxde (LUbuntu), and xfce (XUbuntu) is also nice...
What's even more important than free software? - OPEN FORMATS.