inetinfo.exe / ftp stop responding stop responding same time each week

[poger67]

On wed 4/2/2003 one of our W2K web servers (fully patched, had been running fine) stopped responding to http requests at 17:39 EST. Inetinfo.exe was running in the process list, but no web pages could be loaded. A reboot of the server brought it back (stopping and starting sites in the MMC did not). We went through the machine, found no evidence of intrusion, made sure it was up to date and kept an eye on it. On Tuesday 4/8/2003 at 18:39 same thing happened. This time I noticed that FTP (G6, not MS FTP on port 21) also stopped accepting connections. VNC however was working fine. So now we have 6 days later, same minutes after the hour, same problem. Yesterday, 4/14/2003 at 14:39 same thing. Again, 6 days later, same minutes, but a few hours earlier. Event log shows nothing unusual except for W32time complaining about "repeated network problems" and being unable to update the clock. This is a live web server that we monitor every 30 seconds - other than inetinfo.exe and FTP blocking connection attempts, the have been no network problems. The only scheduled task is TapeWare but that's not until after midnight and has been running fine. Any ideas of where I can look to diagnose this? Any ideas what might be causing it?