The only reason I can think of for this is that you are under the influence of the priest spell 'silence' (if you were in the area of effect if the spell was cast - either by your own party or an enemy). You can't initiate dialogue if silenced - if this is the case there should be a little icon in the corner of your pic on the right of the screen. Have you tried with other party members talking to the guard? The spell wears off after a few minutes.
If this is not the case, it may be a bug - have you downloaded the patch?
I can't think of any other possibilities off the top of my head. If all else fails I know that it's possible to transport your party to the inside of Kalahs realm if you don't mind cheating and have the code for the location - I don't know what that is myself, but others on the board may be able to help in that respect.
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Time is an illusion. Lunchtime doubly so.