Well, this is a known shortcoming of SIMBL. I suppose I have this expectation from OW since I did not have this problem in any of the SPs. I don't know what changed.
For now, I've disabled SIMBL in OW, but this can be a problem. I like using megazoomer
http://ianhenderson.org/megazoomer.html
from time to time since I have a very small screen.
Upgrading my computer is high on my list of priorities, but it's highly dependent on my budget. So, back to Safari for now. :)