GTA IV router trouble

[Muji-FightR]

Hi,

I have a pretty crappy SpeedTouch ST516 router which seems to be having problems with quite a few games.
A few months ago DOD:S stopped working all of a sudden, kept disconnecting or hanging up a few seconds (sometimes minutes) after joining.
I went ahead and found out that it was my router blocking the ports. I forwarded the ports needed for steam and valve games and its working fine since. Beyond me why it worked for several months and went bonkers over night

Anyway, I had GTA IV telling me my router settings are too strict and kicked me out of the game. I just ignored it and played for several hours yesterday without a single disconnection.
Today, it doesnt seem to work at all. I cant find servers, it just puts me into an empty lobby (ie creates one) and sometimes even kicks me out of my own lobby (??).

I googled for it and it seemed to be a common problem among PS3 users but I cant just connect my PC directly to the modem (the router wouldnt let me anyway) so I was looking for the necessary ports to forward.

The official article over at MS says it needs TCP 88 and 3074.
Other forums (including some GTA forum I believe) say it also needs 88 and 443 to work.
Some say both TCP and UDP, some just say TCP.

I'm a little confused now, as I opened all 4 ports on TCP and UDP and it still doesnt work.

Any help is much appreciated

EDIT: Add 53 to the recommended ports, doesn't help either :/
EDIT2: I just disabled(!) uPnP and I was able to connect to a server. After 2 minutes in the lobby I got the 'you're router is using too strict settings' and a disconnect...