We noticed at work after installing Sun Java Client 1.6.0_22, that when you go to open an PDF in IE7, the page is completely blank. So we rolled back to Adobe Reader 10.0.1 and installed the Sun Java Client 1.6.0_22, and the problem went away.
It appears Adobe Reader 10.1 does not like the Sun Java Client. Anyone else with this issue?
No problems with Adobe Reader X and JRE 1.6, but then I am using the latest version 1.6.0_26 - maybe you should try this as well?