Lock up on drop down box on Win 2K pro

I'm on a Novell Netware 3.x network. The 6 users in my directory tree all have Win 2k Pro workstations. They are identical Dell OPtiplex PC's, ordered at the same time and the hard drives were ghosted from one machine. 2 of the machines lock up onoccasion when the user is clicks on the arrow in the drop down box. Example; in MS Word, going to open or save a file, click on arrow in drop down box to choose file and/or location and the PC locks up. The same thing happens in IE v.6.0 when you start to type your web address and the box drops down to show you similar addresses you've recently visited. Here's the really bizarre part - when trying to end the task with TASK MANAGER, the error that pops up is "cannot end (or close) program becauser debugger is running. End debugger and then close program" This becomes an endless loop until the PC is powered down. We have wiped out the hard drives and re-ghosted, updated all programs with every patch and this still happens. One last bit of info, the machines are running a vendor's Oracle based software program. Could that be where this debugger error is coming from? MSSQL Server begins running upon login and in active in the System Tray. We are at our wits end. Please help!