I've just done a forum search regarding this topic, and am amazed to see how many other forum members have experienced the same or a similar problem.
In the past I have manually created a few restore points, usually in periods when my pc was functioning particularly well. This morning I experienced a few strange problems with a particular program, so went to do a system restore only to discover that I had no restore points at all!!!
I doubt that the cause of this problem is disc space, as I have 640Gb, and am currently only using about 20% of that.
I do, however, use CCleaner and Advanced SystemCare 4 quite regularly. Are these programs known to eliminate restore points? I thought they did just the opposite, and created restore points before analysing/modifying or deleting.