I would think by now HP would have got its act together and bought out an updated version of HP Director. IE 8 has been out for quite sometime now. Unfortunately, HP and other makers are usually in the dark as much as consumers when MS make changes to any of their software then its a mad scrabble by their software support guys to find the offending file version update! Believe me it causes them a huge headache, thankfully when they find a solution, its posted within days on their website...
Rather than roll back to IE7, I would first suggest you look at the HP product support pages and see if there is a later version of the director under your psc1355