NextGen Gallery Flash upload no longer functioning

Installed WordPressMU 2.8, installed Nextgen Gallery 1.3.2, everything worked. Updated NextGen Gallery to 1.3.3/1.3.4 subsequently. Everything worked.
Upgraded WordPressMU from 2.8 to 2.8.1 and now the Flash upload no longer functions in NextGen Gallery (the core flash upload for WPmu works fine).

I can upload a zip file via the flash upload.

I can browse for images from my PC, select them and hit ok, but when I complete this, i see a page showing 0% complete and the images never upload.