can you try running the script directly rather than from a bat? we run a number of scripts that fire as frequently as ever 5 minutes up to an hour or just once a day, and the tasks are refered to directly and run just fine. To do this, when you are editing the Actions that are carried out by the task under the Action drop down, select 'Start a program' and under the settings, where it is asking for the program or script to run we have 'C:\Python26\ArcGIS10.0\pythonw.exe' and then the script path/file name is supplied in the text box that asks for arguments. See the attached image.