Keys on Keyboard stop working

Hello,

I hope I put this in the right forum...

I searched for similar threads, but I couldn't find any that seem to deal with the problem I am having.

My workplace is using (among other Solaris-machines) Dell Dimension T3500 as workstations (running Solaris 10 X86 10/09 u8, Kernel-ID=Generic_141445-09). Since our users like the extra Sun-keys (Cut, Paste, Front, etc.), we are using regular Sun USB-keyboards (Type 7, Sun P/N 320-1366-01).

Now for the problem: The users are complaining about sporadically losing keys, i.e. the "Backspace"-key would suddenly stop working, but other keys would continue to work. It is never the same key, and it seems (to me, at least) that non-alphanumeric keys (like Tab, Backspace, Caps Lock and so on) are affected far more often than alphanumeric keys, but I cannot really quantify that. The only way to "fix" the issue that we could find (other than rebooting the entire workstation) is to unplug the keyboard, wait 5-10 seconds and then plug it back in - that would usually do the trick.

We already did some troubleshooting on the issue and here are the results:

Assumption 1: The problem lies in the fact that we use Sun-keyboards connected to Dell computers.
Answer: The issue first appeared when we were still using the original Dell keyboards.

Assumption 2: The problem lies in the fact that (due to the physical layout of the workstations) we have to use 5 metre USB-extension cables between the computer and the keyboards.
Answer: The problem first appeared when we had the keyboard plugged directly into the workstation.

I did a search for this problem, but could not find any hints to fix the issue. I did follow the advice on a USB-related sunsolve-page and double-checked all the patches listed there, but the corresponding patches running on our workstations seem to be the latest ones available.

Any suggestions as to where I can look or how I might be able to diagnose/fix the problem?

Thanks in advance!