i have resolved the problem, it was a precedence issue. because MaxConcurrentExecutables was set to -1, it can only execute 2 tasks concurrently successfully and i had seven. there are two ways around it; 1) increase the value for MaxConcurrentExecutables or redo the execution precedence.
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All it takes, is a step in the right direction, your feet will manage to find the way. I didn't say it'll be easy!!![font="Comic Sans MS"]:cool:[/font]