TS3 Connection Lost

[TemPeR]

my TS3 drops out frequently when there is more then 5-6 people in the channel.
(usually every 5-10mins, depending on the amount of people)

I've tried re-installing my TS3,
I've Port forwarded TS3 for hosting a server and other ports.
Most research I've done says something about firewall.

Help would be much appreciated.