Windows Vista Program Files Directory crashes Windows Explorer

The title says it all... Whenever I open windows explorer, things go smoothly. Unless I try to open the program files directory. The little 'thinking bar' at the top of the window starts to scroll across (the one where the address is typed in) and then explorer encounters an error and has to be shut down.

I thought maybe I had a trojan or malware, but I already went to bleepingcomputer.com and got help there. The thread can be found here:
http://www.bleepingcomputer.com/forums/topic137399.html

It's not a major problem but I know it's not right, and it's got me worried about what else might be wrong. I'd really appreciate any help.

Thanks!!