when you installed, were you prompted for both the cs4 serial number and cs5.5 serial number? or, did you install cs4 and cs5.5?
I was prompted for the cs4 and cs5 serials, I didn't install the CS4 at all this time.
My issue is very similar, except I'm not using a Mac, I'll try to contact the support directly.
post an update.
Well, my problem has just been fixed,thanks to the support chat service of Adobe.
I'll describe the solution for you guys, it might be useful to somebody
The solution consists in going under windows START button, at the bootom left,
then Hold Ctrl key and click on Acrobat X.
You are now able to change a language for Acrobat.
I just had to chose the language to be the same as my Computer wich is french. et Voilà !
PS. thank you @ Kglad for your feedbacks
that's great. and, you're welcome (and, thank you for posting that solution).