[CentOS] centos 5.4, firefox and adobereader plugin, disabled input fields

Hello,

we are using firefox-3.0.15 from the CentOS-Repository and the
adobereader plugin from the adobe-repository. We have a curious problem
with adobereader-plugin in firefox.

When a pdf document is displayed via the plugin, i.e. within a tab in
firefox, all input fields are disabled. I cannot enter a search string
or fill in fields. The cursor and page up/down keys are also disabled.
But when I configure firefox to open pdf documents with the external
acroreader, everything works fine.

Additional notes:
* We are just migrating from SuSE. Some user profiles are working as
expected without problems. Unfortunately, I was not able to figure out
the important files: I traced all of firefox' file operations on the
user profiles, but there are no significant differences between working
and non-working profiles (I just compared filenames, not content).
* the same adobe-plugin works with firefox 3.0.15 from mozilla.org
* I also set up a clean i386-Centos 5.4 from original CD, SELinux
disabled, updated and created  standard user. I only added the
adobe-repository. The same effect, no search avaible.

I would be grateful about a solution (of course :-), but also for ideas
on how to debug this problem.

bye
Waldemar