I just upgraded from Ubuntu 9.10 Karmic Koala to 10.04 Lucid and my Oracle SQL Developer stopped working entirely. I didn't bother trying to look in to it as my SQL Developer was rather old anyway so I downloaded 184.108.40.206 and it didn't work either. Seeing the warnings on the SQL Developer page about supported JDKs I first checked what I had installed.
In the last few days on and off I've been trying to locate a problem with a fairly complicated Perl daemon using POE which was taking a huge amount of time to return a large file via LWP::UserAgent. It's taken a while since in reality we were not doing a simple HTTP GET and the circumstances under which the problem occurs are difficult to set up. However, I've at last tracked it down to taint mode.