I am by no means an expert in this thing, but it sounds like it's either running too hot or not hot enough. If it's able to get a flow started, it's probably overheating. I've read that a dimmer switch can be used to throttle back on the heat, and may be just exactly what you need to keep it running properly.
Shawn, thanks for this fast reply. It appears just as you say. I compared the pics shown on the Lava Lite website and because they do start and run for some time, just as you said "To Hot". I will try the dimmer.
The freezer method is a hillbilly way to cool your lamp faster, taking only 30-40 minutes. But it must be watched, only till it's chilled. The let it reach room temp, run it till hot & repeat.
It doesn't work for all lamps.
Thanks Vixen, I will try this. I don't want to loose them. I have purchased 7 recently and 3 with problems, the new 52 was DOA, from coolstuf.com they have agreed to replace it. They seem like a good Co.