I will assume that it is a type in the last sentence of the second paragraph and that "can upload any book" should be "can't upload any book".
Did you install calibre and select the install USB driver option? If you did this may be the problem as the USB drivers are only required for the PRS-500 and not the PRS-505. There are instructions on the calibre website on how to uninstall the USB driver.
Otherwise, I do not think the problem is in the PC software. Try a hard reset on the Reader. This will, regretfully, wipe out all the books you have loaded on the unit. I had to do it once. There are instructions on that in the manual on the CD.