Just a general passing of information, last week I was in Cayman Islands and Honduras and I tried to send an "OK" message from my Spot Messenger but was unsuccessful due to the lack of a position fix.Later in the week I was successful in sending a signal from the Yucatan. Prior to this recent failure I have been successful sending the "OK" message on numerous occasions throughout the US and the offshore waters of the midatlantic. The failure was not an operator error nor was it due to a lack of good coverage available according to Spot's area coverage map. When I returned home I contacted Spot and they advised if this happens again, not being able to obtain a fix, ( the blinking lights on the unit will indicate this) to turn the unit off than back on again. This proceedure is not explained in the operators manual and I have not had the occasion to try it.