Connection lost to SBS2003 services using WLAN

Hi colleagues,

I’m getting a pop up message every certain period of time asking for credentials to access SBS2003 server even I mapped network units before correctly.

Outlook 2003 client is also losing connection to the server many times a day.

I’ve detected this problem in the network clients using Wireless. Wired computers do not have this issue. Wired computers uses DHCP provided by SBS. Wireless computers uses static IP addresses (these addresses have been excluded from DCHP range). Do you have any ideas on how to get this issue fixed?

Thanks in advance,