Ok, try this:
${SQL:SELECT Value FROM CustomPollerStatusTable INNER JOIN CustomPollers ON CustomPollerStatusTable.PollerID = CustomPollers.CustomPollerID WHERE UniqueName = 'GBAvailable' AND UniqueID= ''' & ${UniqueID} &'''}
that is ' 3 times with no spaces.
(This is just a guess, and I could be miles off...)
