I worked with firewalls and found out about a secret long ago. There is an external connection TCP to playonline that keeps randomly calling out. This connection is separate from the actual game. If this connection fails a few times it'll see the connection auto dropped. Even though the game is still running smoothly the client and server DROPS the connection after a set number of fails.
The game runs on mostly on UDP packets. The sub intermittent connection is based on TCP packets.
What you have is most likely something in between dropping packets. It could be you local hardware or an in between WAN connection issue. I suggest you do a Traceroute and or pingpath to the SE game severs. This will most likely point you toward where the failures are at. You might also want to look at your modem and router logs to see if you have intermittent sync issues where the internet or encapsulation is failing from the errors.
It all depends on the type of connection you use. In a lot of cases if people are on a wireless network that's the 1st place to check. You could also try a free site this like this. If you really want to get serious connectivity help I suggest www.dslreports.com!
On a side note. I had an issue like this where it was a DSL line that had bitswapping turned on and the DSLAM was incompatible with it. What would happen is the line would connect fine but over the course of a few minutes the line would start building up errors until it went out of sync. When this happened the modem would drop sync and reestablish a connection. In normal web browsing thas was barely detectible because the modem would re-sync in a matter of seconds. The game would stay connected but the router would count these and after a few of them it's eventually cause the dynamic IP to change. When this happened the game wouldn't recover EVER.
After I made the minor DSL adjustment I rarely ever got disconnected. The connection became ROCK solid even during thunderstorms.
Hopefully you all do some research and testing on your end to narrow down the issue. I don't think its a cut and paste issue. The generic help in previous post didn't cover much at all other then the one from RAIST. I hope mine sheds some interesting light on the VDSL/ADSL side.