Gee... and I thought it was something i did wrong. I've had the samething going from day 1 with 3.50.
The "fix"? Turn off accounting. Sadly, I USE the accounting, so that's not an option.
Seriously, it looks like accounting has serious problems in 3.50.
Looking at the logs, it appears that accounting dies on a fairly regular bassis. The data I'm getting back from it doesn't even come close to matching the data I'm getting from the switch port that the firewall is plugged into. Much lower... litle it's not collecting 24x7 like it should.