Hey guys - after i was gettings error 9000 and 4001 every 10-20 min. i decided to dig into this matter, cause it seems to be a local problem and not a server side problem.
This is what i did and have had zero issues for days now:
1) Startup SWTOR and join a server
2) Alt-Tab back to windows
3) Startup Command-Promt in Admin mode
4) Type in the following: Netstat -n -p tcp -b | more
5) You will see a line like this: TCP XXX.XX.XX.XX:***** YY.YYY.YYY.YY:**** ESTABLISHED ZZZZ [swtor.exe]
6) Write down the port address for the local and server side
7) Quit SWOTR
8) Now log on to your router/modem configuration and add the following to your NAT/port forwarding settings: Internal port = "local port" and External port = "server side port" and Protocol = TCP and IP address = "your local ip address on the machine"
9) Save settings
10) Startup SWTOR and see if it helped.
For information i have also port forwarded the officiel suggested ports for the game.
Hope that this information will help some of you guys ;-)
Regards