IIRC you're on v7.7.5, the general patch to stop this issue would be to convert the two memory tables in the database (_ONLINE and _TOPIC_VIEWS) to be a MyISAM type which will write the data to disk vs keeping it in memory which will give you the errors you're currently experiencing.

Some reading:
Very weird error this morning.
We Encountered A Problem: ubbt_ONLINE is full. SQL Error 1114

I am a Web Development Contractor, I do not work for UBBCentral. I have provided free User to User Support since the beginning of these support forums.
Do you need Forum Install or Upgrade Services?
Forums: A Gardeners Forum
UBB.threads: UBBWiki, UBB Styles, UBB.Sitemaps
Longtime Supporter & Resident Post-A-Holic
VNC Web Services: Code Modifications, Upgrades, Styling, Coding Services, Disaster Recovery, and more!