i noticed when changing googlemail settings to always use https; on many occasions it will stall and fail
no wonder it's still beta..
if you've recently changed gmail settings to always use https..then while mail is loading, quickly click on basic html before it loads.. when you're in basic html..click on settings and select do not always use https.. if you check your mail from home and not a public pc, this will not be a security risk.
if that's not your case..and you're sure the problem happened only when you've updated to 1.5.2, then you might have a bad connection/pipeline in prefs from older version profile conflicting with latest km.. then, create a new profile(edit>manage profiles> new>ask at startup check).. run kmeleon with new profile with all default settings and see if you can access googlemail properly.. goodluck