Karre:

The most likely reason is some kind of timing difference. The second most likely reason is that the transactions that should be in the GL are missing.

You mentioned "...match the consolidated amount in the G/L" If you are consolidating the transaction this makes it very difficult to reconcile and find any errors.

You didn't mention which report but I believe all of them allow you to select a date range. Run the report one period at a time and compare to GL. Hopefully you will find one month that is different and be able to track it down from there.