4
Well with that many users it is clearly a server platform, whether Windows or Linux/unix based.
I could see where bandwidth would be an issue with a forum that active. But I don't quite understand where the error message itself is coming from. Of course on a great day I don't get 1/6 that traffic.
If it is a XOOPS forum or XOOPS error itself I am sure the developers will know where I comes from. I myself have never experienced it.
Added: now I see your edit. I have seen discussion of that database factory error before on the forums. Maybe try a search on that.