[ns] plugin for ns2.34

hi,
I have ubuntu 11.04, gcc 4.5.2
I need to install cgal-2.4 to add a plugin in ns2.34
to do that i need gcc 2.95 or gcc 3.0
when triying to instal one of them, i always have error when making
can any one tell me how to process?
should i unistall gcc 4.5.2 or what?
thkx
Fatma