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The thread that manages Checker tasks on the server automatically kills tasks that have run for too long (default is 5 minutes) to protect the mobileOK Checker from potential infinite loops. When the Checker is run in asynchronous mode, the poll for update the client sends every few seconds will automatically re-create the task if it does not exist anymore. This means a page that requires more than 5 minutes to be retrieved and checked is likely to create an infinite loop (well, it stops whenever polling stops, i.e. when the client closes the tab).
I can't check http://www.dongolahouse.co.za/ It gets as far as "The address is being checked. Please wait..." and then you wait forever (tried Opera & Chromium). Without any further feedback I can't tell what the actual problem is or if it really is related to this bug.