Usenet causing AOL LLU to disconnect

I'm finding that my AOL LLU connection is disconnecting and then reconnecting whenever I connect to my usenet server. It does just seem to be when i fire up my newsreader and it starts downloading binary files. I have a netgear DG834G wireless router, and checking the logs, it says things like
Tue, 2006-10-24 11:54:37 - LCP down.
Tue, 2006-10-24 11:54:39 - Initialize LCP.
Tue, 2006-10-24 11:54:39 - LCP is allowed to come up.
Tue, 2006-10-24 11:54:54 - CHAP authentication success


However, I dont get a log entry like this everytime the connection burps - sometimes there is nothing in there, but I still find that my IM clients disconnect and my usenet connection goes down with a "Authentication failed" error message. Giganews tell me according to their logs, I'm reconnecting from a different IP address (which they block for a few mins to prevent abuse), which would indicate that I'm being disconnected and am reconnecting.

I've tried both pppoa and pppoe, as both are supported on the AOL LLU network. I've checked all my other settings, and I dont see anything obvious - so does anyone have any tips on what could be going wrong?

Thanks

David