Several other people have reported this, but I haven't seen a solution yet. Could you take a look through the discussion in these threads to see whether anything there helps or whether it suggests new avenues of exploration:

• Active Tab has floating chinese characters as well as the tab name how do I get rid of this?

• Asian words poping up on the Menu Bar and Tabs on Firefox Why?

Try to open a new window to see if that new window works better.

See also this thread about a similar problem.

• [/questions/1027393] Active Tab has floating chinese characters as well as the tab name how do I get rid of this?

Separate Issue; Your System Details shows;

Installed Plug-ins

Adobe PDF Plug-In For Firefox and Netscape 10.1.9 Adobe PDF Plug-In For Firefox and Netscape 10.1.1

Having more than one version of a program may cause issues.

Some added toolbar and anti-virus add-ons are known to cause Firefox issues. Disable All of them.