How to do it again? I had simply forwarded needed ports (e.g. for counter strike, ftp, http etc)) but now with same system, same OS and same router and settings, it's not working. Tried setting router to "factory defaults" and do everything again. However other jobs are being done like it is connecting to my DSL ISP and I can access Internet easily. Still no success. PS. I tried on both Windows and Ubuntu. On Windows I use it for Counter Strike and others (e.g. host my local FTP server) on Ubuntu.
Stupid question, but need to check - are you using DHCP?
It is possible for your IP to change and then you need to manually redo all the ips that the port forwards to.
This is the most common reason for when everything is working, no updates have occurred but there are similar symptoms to what you said.
So, the solution here is to either use a static IP on your machine or do DHCP reservation on the router.... Or you can carry on doing it through standard DHCP, but be prepared to change whenenver your lease expires as does not get renewed as the same.
make sure you're using static IP addresses and the settings are corresponding with the router's port forwarding settings.
for the correct router and software settings, refer to portforward.com
consider a 3rd party firmware such as DD-WRT, you'll get much more out of your router.