Well, I don't get them on any of my machines.
There may be merit to the speculation the problem is with ads. Some of the ads I see are related to other interests outside of RV and ham radio so I suspect I'm seeing my own customized set of ads, which are different from what you are seeing. Can you get an idea what ads are up when the error appears?
It is encouraging to see the vBulletin runs OK in the browser once you have clicked the pop up. Which makes me think again it may be the ads.
If I get the message I'll have a poke at it. Until then, sorry, I can't fix what I can't reproduce.
Question: How often does this occur? On every page or just when you first log on?