What locale and encoding are you using?
Evidently the LIKE index optimization is failing, but I would
not have guessed that a string like 1:0: would cause a problem,
especially not if all the entries in the column contain just
digits and colons.
You can find plenty of material about LIKE+index problems in
the list archives. For 7.1, we've gone so far as to disable
the optimization altogether in non-ASCII locales (and I'm sure
we'll get complaints about that, too :-().
regards, tom lane
