4
I don't think that it is a bug. The current value for "Bad counts for Crawlers" is set at 40, i.e. if you have more than 40, you'll get a blank page.
I have normally tons of tabs open with XOOPS pages, but I never got a blank page, so I guess, I was below 40.
If this is on your local site, try to increase the value for "Bad counts for Crawlers" and see if it helps...