I am running Vista Ultimate 64-bit. I have experienced numerous lockups with Reader X, since installing. For instance, if I go to "Help/Adobe Reader X Help", nothing happens and Reader X locks up, requiring it to be forced closed.
Also, I have experienced a similar issue with a PDF where I have added Comments and saved it. When attempting to reopen the PDF, Reader X locks up again.
I've tried checking for updates (I'm setup to automatically download updates), but it says no updates available.