The setting of the running status in the cron_schedule table in Magento 1.4 is not working correctly. The code in Magento 1.4 is not 100% correct. Create a local copy of Mage_Cron_Model_Observer and take a look at the dispatch function:

The status should also be saved here, not just the execution time. Change the code from the above to the below:

Setting running status correctly in Magento 1.4
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