I was running ART on a CallManager with 3.0(8), and it was still getting new data after it was upgraded to 3.0(9). I haven't talked to anyone that's had this problem.
Do you have more than 1 CallManager in the cluster? If so, is it possible that CDR is not enabled on the CallManager that the phones are actually registered to?
If you are comfortable with SQL, you could go into Enterprise Manager and compare the latest date/time stamp in the CDR database with the latest date/time stamp in the ART database.
The formula to convert from the date/time format stored in CDR to a normal date/time is most easily done in Excel. Here is a quick way to translate:
Put the number in cell A1, and in cell B1, type in:
=(A1/86400)+DATE(1970,1,1)
Then change the format of column B cells to be date, where it displays the format M/D/Y 00:00
Note that the time using that formula will be the number of seconds since Midnight, January 1, 1970, expressed in UTC time.