Down Network

I have a network that goes down everyday between 3:30 and 4:30, all the workstations can no longer connect to the win98 server. There is a Linksys 8 port 10/100 hub and most of the time we have the problem both top and bottom lights are blinking. Resetting the hub and all is well. If the linksys is not blinking then we find the server shutdown, rebooting and no scandisk. What gives?