Been chasing regular high CPU usage by NIS, PC is pentium 4 running XP, 3Ghz, 2GB RAM and Service Pack 3. Problem has been seen for 6 months or so and results in the current application freezing for approx 10 second every 6 minutes. Seems to have started towards the end of NIS 2012
I had Norton connect and they did a manual removal of NIS and reinstall
It doesn't occur continuously, there may be breaks of some hours so tried keeping a record of the applications running when the problem occurred. Eventually found that it was when Outlook Express checked for new mail. I use two ISP with three accounts, the time for doing the check was set at 5 min but they are actually occurring every 6 min and trigger the CPU spike.
As OE is getting old I switched to Thunderbird and get exactly the same result. The duration of the 100% CPU spike by sscvhst.exe is the same regardless of the number of accounts contacted to recover mail, I haven't sent myself a very large e-mail to see if size has any effect.
Turning off Check Incoming E-mail in NIS settings prevents the spike.
I can't see any way to limit the enthusiasm with which NIS checks mail but note that Pulse Updates which actually bring in data use something like 60% CPU and have no discernible effect on the running application.
Would be interested in comments from someone using a similar PC or whether others chasing high CPU usage can link it to their e-mail client