UPDATE (28 June): After searching, saving and downloading tests in ARTstor, it appears that they have fixed the compatibility issue with Firefox 5.
If you are a PC user with Firefox as your default browser, you may be prompted (sometimes rather urgently) to upgrade to Firefox 5. Unfortunately, at this time ARTstor is not compatible with the latest Firefox browser. ARTstor is aware of the problem and is working on a solution, but in the meantime either postpone the upgrade (do not check for updates) or use a different browser (click here for information on supported browsers). Thanks for your patience and we’ll keep you posted on ARTstor’s progress.