Double bandwidth reporting on multilink interface

Hi,

I have a couple of Cisco 2821 routers running 12.4.24T7 code. Netflow set up currently as version 5 and monitoring traffic on a multilink interface. The multilink interface is 4 x 2Mb E1's.
On the far end of the link I have a 3945 which is showing correct utilisation, but on the 2800 it reports as double utilisation (compared to that shown on interface itself and to the utilisation reported by netflow from the far router). I notice there are a few options for eliminating double bandwidth problems such as encrypted interfaces, but nothing suggesting there should be similar problems on a multilink interface.

Any ideas?