Having another thought on this and maybe downgrading Adobe Flash may have benefits and it is worth a shot.

1) Uninstall all Adobe products via the Adobe Flash uninstall tool http://kb2.adobe.com/cps/141/tn_14157.html *note: turn off all flash related programs*
2) After you have uninstalled all Adobe Products successfully, Reset IE or your Internet Browser settings.
for Internet Explorer: Click Tools (from the menu bar), then select Internet Options, Click Advanced Tab then hit Reset Button. WARNING! This will reset your IE settings and will delete history, cookies and form autofill.
*Also, make sure to delete all Browsing history by selecting Tools> Internet Options> Delete button under General Tab.
3) Reboot the computer is a must!
4) After successful reboot, Install an archived Flash Player version from here http://kb2.adobe.com/cps/142/tn_14266.html
5) Reboot computer again for the last time.
6) Try loging-in to the site.

Hope this resolves the issue.