Stick the SSI call in one of your main non-forum HTML pages and you'll find it updates fine. SSI calls don't work from inside the forum unless you pre-define them as per the 'show IP' hack (Remote Address).
I suggest you read this thread right through as you'll see exactly what I did a page or two back to resolve this.
Donate to UBBDev today to help aid in Operational, Server and Script Maintenance, and Development costs.
Please also see our parent organization VNC Web Services if you're in the need of a new UBB.threads Install or Upgrade, Site/Server Migrations, or Security and Coding Services.