DC every 1h

[Ariun]

We've got instant DC every 1h.
I'm running 2 accounts in parallel, my mian character + box. Both are in town and trading.
I have 2 PCs, as I play together with my wife. She's running 2 accounts too. It seems that regardless if my characters are in town or exping, I've got DC every 1h.
I can't trade anything this way (yeah yeah, I know, buy offline shop item). But that's not a solution to a problem.
Sometimes I've got instant DC in the middle of exp, but it's a bit more rare then 1h (like once in 2-3h).
Is it possible that the system thinks, that I play 4 chars on one PC? (while it's 2 chars on 2 PCs, 4 in total).
Or is it just a timeout issue when the character is idle (trading)?
Anyone have similar problem?

Btw. I live in Sweden, and have pretty decent internect connection (100Mbps). Didn't tried to disable firewall or the antivirus yet, but I doubt it could matter.