Windows XP Pro Shows netdrive (q in this case) Full and will not map

Have Dell xion 2850 over 150 gig on netdrive. It is dhcp with 19 work stations showing netdrive (q) almost full, and will map to the netdrive. The three remaining workstations are unable to map. Error says the server may be busy. and they show the netdrive completly full, under my computer, which I know it is not.