IE7 javascript issue. Firefox displaying fine. Repair?

I have a client with a 2-week-old Dell desktop running Vista. I recently set up his home network which included a wireless-n router and a linksys wireless-n usb dongle. I ran into issues getting the dongle to connect to the network. During my troubleshooting I uninstalled McAfee Security Suite that was pre-installed on the Dell. I thought its firewall was causing the issue.

After I resolved the wireless network issue (bad router), I tried to install McAfee for him again. When I put the CD in, all I received was an installshield window with the McAfee banner and the "cancel" "next" and "back" buttons all unclick-able. The buttons themselves were all labeled "label" and not "back" "cancel" "next". I thought it was just the CD, but the download from McAfee gave me the same weird window.

Because of the time of night, I opted to install Symantec 10.2 client which installed fine. When I opened IE7 to show him how to check OWA, the main issue for this question appeared:

The runonce that IE7 gives users was just its blue background. No errors, no nothing! I then went to our company's Kaseya portal to see if he could remote into his work machine. The portal loaded 100% blank. I could not even get to its login page. I noticed that both pages are (i believe) all javascript. I checked security settings and reset them to default just to be sure. I am able to open the pages in Firefox (which was already installed by him) without any issue. Unfortunately, Firefox is not an option for his work-centric activities, nor is it working well as a temporary band-aid.

I guess my ultimate question is how can IE7 be repaired in Vista without using the OS install CD. I really don't want to have to go back to his house if not needed. I've searched high and low and haven't really come across any tips or solutions for repairing IE7 in Vista; only XP.

This is my first question on E-E as a member, so please let me know if I should be including anything else.

Thanks!
-E