Luckily the fix is easy...
sudo apt-get install xulrunner
Then you'll need to either edit or create a startup script for Aptana to use. So make a file called "runAptana.sh" in /usr/local/aptana and inside that put...
#!/bin/bash
export MOZILLA_FIVE_HOME=/usr/lib/xulrunner
/usr/local/aptana/AptanaStudio
Then, whenever you want to run Aptana use that script instead; otherwise you'll get those nasty errors which hamper your daily work efforts!
