It's a dramatic thing to do, but in a similar situation I have lead a move to another hosting provider and new site when this happened at another site I used to frequent.
The site was old and buggy and starting to get overrun by spam. The owner was unresponsive and AWOL so we all left en-masse and set up a new very similar site that I created on my hosting provider. After we all left and the site got completely overrun, the original owner closed his down and transferred all the data from the site to me, which I merged into the new site - so preserving all that had been built before.
I would be willing to provide the hosting and setup and do the same again if there is enough interest here to do the same.
The current site is
http://www.thehistoricdistrict.org if you want to take a look - it's a site for those who love and restore old houses.
Without the upgrades It will only be a matter of time before this forum is overrun by spam or simply fails altogether