Either it doesn't like you or you have do-nothing enabled... Just kidding... one of those days...
A couple of things... does this happen to ALL PDFs? Even ones on your desktop?
If not (desktop works) you are having browser integration issues.
If so (both broken) - launch Reader w/out a PDF and see if the EULA message comes up.. you have to say 'YES' to the EULA for it to work.
Finally, you have to have the current version of Flash installed with Reader. Reader no longer has Flash baked in.. and relies on the external version.
If none of that works, download R10 from the Enterprise Deployment area (google Adobe REader Enterprise Deployment Download) - you should find it buried there.
Hope some of this helps.