Explorer Bombs Out

When attempting to access a network folder or file, Explorer simply closes (disappears) and eventually drops you back to your desktop. The error in Event Viewer reads:

Faulting application explorer.exe, version 6.0.2800.1221, faulting module ntdll.dll, version 5.1.2600.1217, fault address 0x000080db.

What causes it and how do I rectify the problem? Keep in mind that the latest updates, including SP’s, have all been applied prior to this development.

Again, the OS is Windows XP Pro including all updates and Service Pack.
The computer has been functioning fine for MONTHS. This just began to occur TODAY!