First I will clear the Caches, Internet files and cookies, then scan for
malwares on that machine to be sure all clean.
Then go to Start >> Control Panel >> Network and Internet connections >>
Internet Options.
On the IE Properties click on Advanced Tab and scroll under Browsing option:
[&] Browsing
   [   ] Disable script  Debugg  (Internet Explorer) check this
   [   ] Disable script Debugg (other)   check this box
   [   ] Enable  Third-Party browser extensions  (Req Rest)
Then click on Programs Tab and click Manage Add-Ons and Disable all
non-Verified Add-Ons ( you should Renable them later one-by-one and which
will be the culprit and Remove it or leave it disabled.
Click Apply then OK and Reboot.
Do you have other toolbars installed ?.
HTH.
Let us know.
Regards,
nass