Hey there:
Older versions of Tomcat 5 had a bug where the class files weren’t mapped correctly to the source, there is a workaround (sticky) in this forum, or you can upgrade to Tomcat 5.0.18 (this is my suggestion). Secondly, as far as runing out of memory, if you aren’t passing custom VM params to Eclipse to give it more ram (256 lets say) then yes I’ve seen instances where people run out of memory (Especially with lots of plugins loaded, or a few heavy ones). You can give Eclipse more memory via the “-vmargs” command line param to the eclipse.exe (or eclipse on *nix) file via your shortcut (or script):
eclipse.exe -vmargs -Xms128m -Xmx128m
if you have 1GIG of ram, I think Xms128m and Xmx256m would be a good setting for you.