Microsoft Windows Network: Drive already in use error??

Im getting this error on two laptops on the network on almost a daily basis

“An error occured while reconnecting S: to \\192.169.0.9\Sales & Marketing

Microsoft Windows Network: Drive already in use

The connection has not been restored”

The 2 laptops are both running XP and connecting to Server 2003

Any idea what can be causing this error or a solution to solve the issue?