[eluser]BrianDHall[/eluser]
I've run into a lot of pain with PHP 5.3 myself, with out without CI at all. My XDebug on Vista 64-bit wouldn't work no matter what I did, CI throws lots of deprecated errors about stuff I don't even understand why it would be deprecated, etc etc.
I fixed all these issues very simple - I went back to the latest version of PHP 5.2. I think a new version of CI might be needed to fully address all PHP 5.3 issues - you might consider a bug report on that one though after looking into it a bit.