Question : window 7 OS:  blank (black) screen only, as it logs in

This is an Inspiron 1440 Dell laptop with Windows 7 Home Premium.  It boots up normally and then just as it gets to the desktop (automatic logon), the screen goes blank (black - no icons, no start button, etc).  I can open task manager and run some things - like mmc,etc.  I can't seem to run explorer.exe though.  After 10 or 15 minutes, the screen saver comes as it should, appearing correctly.
( same behavior occurs in Safe Mode )
I've updated the BIOS to the most recent version (A07). I've run all the Dell built-in diagnostics and everything passes.

Answer : window 7 OS:  blank (black) screen only, as it logs in

When you say you can't run explorer.exe, is there already an explorer.exe process running?
If so, try ending that one first and then running explorer.exe again.

If that doesn't work, and system restore isn't disabled, try running:
%SystemRoot%\System32\Restore\Rstrui.exe

And taking it back to a previous restore point.

If you've got a windows 7 dvd, try booting into that and:
 - Click "Repair Your Computer"
 - Select Windows 7
 - Select the recovery tools option
 - Run the startup repair

See how that goes.