Is there a way to automatically flush the policy logs after reimaging a machine? I have scripts that are using the "startup" trigger and the "Once per computer" frequency that I would like to have run again once the machine is reimaged.
CasperSally is correct, any policies that had previously run on it that were set on a "once" type basis will not run again unless you flush the policy history for that system, because Casper Suite uses the MAC address to identify systems. So even if it got a new name, new OS on it, etc, it still sees it as the same Mac that already ran those once per computer policies.
You can also overcome this issue with things like Extension Attributes, Smart Groups and ongoing policies, but unless they are set up that way, flushing the policy history for that Mac is probably your best bet.