Windows 7: Very recent problem with Service Event Notification Service

Booting up on my Windows 7 Home Premium 64-bit has become very slow, and a caption about Service Event Notification Service appears eventually in the bottom right-hand corner after a couple of minutes of blue screen. Looking at the event log doesn't seem to show anything. I've run a Kaspersky virus scan and also run the system disk check, and both were clean. When I resorted to a system restore it worked on first boot, but when I logged on today the problem reappeared. Has anybody encountered this problem before? Any good advice would be gratefully received. Thanks for reading.