Trouble with Android

[Ben Rubinstein]

Hmm... attempting to do some very simple trial stacks on Android, after not 
having done any for a long time - having fought my way through a few 
strangeness with regards to expired debug certificates and the like, I now 
find that all my stacks - built with 5.5.3 or above - simply display black, on 
two different test devices.

An older version of one of the stacks, an APK I happen to have lying around my 
hard drive that was built about 14 months ago, can be re-installed and works fine.

Do I need to re-install the Android SDK if I haven't done so for over a year? 
  Or is there some other obvious thing that someone can tell me I'm doing wrong?

Many thanks,

Ben