samba - May 2004 - intermittent slow connection smb domain controller

hi im running a network of around 25 win98 clients off a smb 2.7 domain
controller.  every couple of days we experience a period of very slow
connection speed - accessing network shares and mail etc.  the logs on
the domain controller produce the following error message during these
times.

kernel: eth0: Too much work at interrupt, IntrStatus=0x0010.

Im thinking perhaps i need a backup domain controller to cope with the
load?  would this be right?

thanks for any help 

shaun