file open file save dialog freeze hang all applic

Dear Colleagues,
Whenever I request a "File|Open" or "File|Save" from any application, the mini-Windows-Explorer dialog box that opens freezes and hangs the entire application. The dialog box is not populated with the existing files in the default directory, the column headers are blank, and the dropdown arrows adjacent to the column headers are distorted. This failure of "File|Open" and "File|Save" occurs in all Office 2003 and Office 2007 applications, in MS Outlook 2007, in Adobe Acrobat 7 Professional, and other applications. I can only open MS Office or PDF files by double-clicking the filename in a full-Windows-Explorer file listing. Perhaps the mini-Windows-Explorer subroutine is corrupt. Any way to restore it? Cntrl-S still works for saving existing files. I am logged on as an administrator.
Thanks very much!
Lightfoote Dell Opliplex GX 280 RAM 2 Gb DDR 533 SATA 80 Gb 3.2 MHz Processor ATI FireMV2200PCIe with video RAM 128 Mb; Rating = 3 (!)