After having problems with a nightly a few days ago, I re-installed eclipse from scratch (Europa J2EE version), and Aptana Studio and Pro.
My update policy is set to 'Stable Release Candidates'.
This morning when starting eclipse I was informed that an Aptana Studio Pro update was available, but when I selected to download and install the update, it produced an error message stating that the 'Result Configuration Does Not Contain The Platform'.
I therefore cancelled the update and attempted a Help>Software Updates>FInd And Install.
I was told that an Aptana Studio and Aptana Studi Pro Update were available - when selecting the Pro update, I get the same error ('Result Configuration Does Not Contain The Platform'), if I select the Aptana Studio update I get a 'Configuration Problems' error.
I didn't see this as a Major or Critical bug hopefully it will help you.
Regards,
Dan