Audio devuice givibg problem

Hello,

The problem is in a call centre dialing vide eyebeam .After 2 to 3 calls in few PC's the computer gives an erroe message no audio device present. On restatsing the computer it works fine for 2 to 3 calls then again the same problem arises. Is this because of some sort of virus . On re formating one of the PC it worked fine for 10 days then again the problrm aroused
Pls. help.