Slow opening look in combobox

The problem happens when in any application on win2k pro and clicking file open. When you then click on the lookin combobox to bring up the drives, there can be a delay of up to 10 seconds.

The doesn’t happen all the time, only if Windows Explorer is not used for as little as ten minutes.

It sounds like a powermanagement problem but as far as I can see I have disabled powermanagement on the Harddisks and network card.

I was wondering if anyone else has the same problem or even an answer.