Have you tried restarting one of the effected clients? if so dose it fix the issue?
Have you tried changing the reporting time in ARD for the client?
IE: in ard select one of the effected computers. Get info on the client, click on the reporting tab. click the edit button. Make sure the current day of the week is checked in reporting. Set the reporting time to a few minutes ahead of the current time. click done, wait till the set time passes, Then try running the report.
Have you tried a safeboot on an effected client, restart, and then try running a report.
Is your OS up to date? if no, have you tried updating the os, and thent ry running a report.
When you say, "No scheduling on the report, run live." are you saying you haven't scheduled a reporting task; or are you saying the default offline reporting policy for the client record in ARD is set to not run at all?
Because i'm saying if modify the computer record in ARD to include a default offline reporting policy to run a few minutes from now, then that offline reporting policy may be able to jump start reporting. At witch point you may be able to run your report with run live or schedule.