Local Scheduler Not Working On All PC's

Hey everyone,

We have deployed a new client to a few thousand PC's and are noticing that the locally scheduled tasks (vulscan and inventory scan) are not running on some PC's.  The same client went on all systems so we don't suspect anything with the client.  I know this is a pretty broad question but can anyone offer any suggestions as to what would cause the local scheduler to fail running on some systems?

Thanks