A lot of folks who’ve been using PSE 6 for Mac for a long time with no problems at all are suddenly finding themselves confronted with a blank white window when they launch the program now. It’s a problem with the Adobe registration servers and the fix is easy, if not obvious.
Just disconnect your Mac from the Internet (turn off wifi or unplug the cable) and start PSE 6 again. This time you should see the Registration window. Choose “Never Register” and all is well (this won’t remove your previous registration from your Adobe records, and in any case, registration for PSE 6 was voluntary, unlike later versions that require it).
The Adobe kbase document about this:
(Thanks to Elements forum user R_Kelly for first figuring this out.)