black screen after windows login; mouse is there

Hello

Sometimes when i restart or power up my Inspiron 530 desktop, the reboot process goes flawlessly to the windows login screen.  Once I enter my windows password, I get a black screen instead of the desktop.  The mouse pointer is there; I can move it all around, and when I use Ctrl-alt-del, the screen comes up that gives me the option to lock the computer, start task manager, change password, etc.--it's all there.  From there I have to restart my computer several times until finally the desktop shows up.  Once I get the desktop to show up, I don't encounter any problems doing anything.

I am using the ATI Radeon HD 2600 XT video card with driver version 8.402.0.0--this is what came with the computer when I purchased it.

This may not be a video problem, but it seems to me like it is since Windows is working behind the black screen (the mouse pointer is there; C-A-D works).

Any ideas?