Plasma Desktop INSANELY slow since switching to KDE 4.7.0

I’m running Opensuse 11.4 on a Dell Inspiron 17R, Core i3 350 CPU, Radeon 5470 Graphics (fgrlx driver), 4 GB RAM.
Since yesterday and KDE 4.6.5 everything ran smoth and fine.
Then I installed KDE 4.7.0 by switching the installed KDE software from the 4.6.5 repositories to the new 4.7.0 ones.
Installation worked fine and without problems. Bu tafter rebooting the system, the Plasma Desktop ran INSANELY slow.
It took (and takes) about 15 minutes to start after logging in, and each time several minutes until Icons, applications, and so on are displayed.
The desktop (and system) is unusable like that. I even turned of desktop effectss and OpelGL and switched back to xrendr, without major changes.
Looks like its only plasma that’s affected by this, because applications mostly work fine internally
Today I tried switching back to KDE 4.6.5 (just the same I did yesterday the other way round) but the problem persists.

Any Idea how to solve this problem?? (Before I reinstall the whole system … :frowning: