I can assure you these are not intentional changes.

The slowness and the strange mouse responses might be related, but this is the first report I've read about them, so I'm not sure what's going on there.

To quickly determine whether this might be a settings issue, you could try this 3-minute experiment:

Create a new Firefox profile

A new profile will have your system-installed plugins (e.g., Flash) and extensions (e.g., security suite toolbars), but no themes, other extensions, or other customizations. It also will have completely fresh settings databases and a fresh cache folder.

Exit Firefox and start up in the Profile Manager using Start > search box, or Run (hold down the Windows key and press R):

firefox.exe -P

Don't delete anything here.

Any time you want to switch profiles, exit Firefox and return to this dialog.

Go ahead and click the Create Profile button, give it a name like Nov13, and skip the option to change the folder location. Then start Firefox in the new profile you created.

Until you go back to the Profile Manager and start up in your regular profile, your desktop shortcut should fire up the new profile.

Does the mouse or keyboard behave any better?

Note: When returning to the Profile Manager, you might be tempted to use the Delete Profile button on your new test profile. But... it's a bit too easy to accidentally delete your "real" profile, so I recommend resisting the temptation. If you do want to clean up later, I suggest making a backup of all your profiles first in case something were to go wrong.

In case old/inconsistent files have accumulated in Firefox's program folder, you can replace the program files without disturbing your settings using this Clean Reinstall procedure:

(1) Download a fresh installer for Firefox 33 from https://www.mozilla.org/firefox/all/ to a convenient location. (Scroll down to your preferred language.)

(2) If applicable, exit out of Firefox or make sure it is fully terminated in Task Manager.

(3) Rename the folder (64-bit Windows folder names)

C:\Program Files (x86)\Mozilla Firefox

to

C:\Program Files (x86)\OldFirefox

(4) Run the installer you downloaded in #1. It should automatically connect to your existing settings.

Any improvement with mouse or keyboard??

Note: Some recently installed plugins may exist only in that OldFirefox folder. If something essential is missing, look in these folders:

• C:\Program Files (x86)\OldFirefox\Plugins
• C:\Program Files (x86)\OldFirefox\browser\plugins

Thanks for the answer. Currently I have reverted to 32.0. The upcoming days I cannot test, because I need a stable and non-lagging) browser for my work (over Citrix connection).

Once I have the time I will upgrade (again) to 33.1 and perform some more tests (from the observed behaviour in 33.1 I suspect that the autoselection actually is done, but their is no visual sign of this) and follow your suggestions.

Q: Will creating a new profile "kill" my Citrix ICA Client?

I will report back in a few days.

Bart

Setting layers.offmainthreadcomposition.enabled to false seems to have resolved this issue. The setting of hardware acceleration has no influence on it.

Both possible solutions were found on this forum, so thanks to the community!