I actualy posted my problem in the GEneral Mac Problems Forum, sorry for that, wanted to get here, but I don't believe that anybody too troubled about it, because there was no reaction at all. Perhaps somebody is able to help. I tried nearly everything that's in the book, installed, deinstalled, but nothing worked. So, what I wrote was:
I'm afraid of not being very entertaining stating same connection problems as anybody in this special forum. from one moment to the other LW stopped working after a half year of successfull use.

1. Os: Mac OS 9.2.2
2. Internal Mac Firewall Doorstop, no difference if turned on or off
3.288 Mb
4.220 Gb
5. DSL Cable
6. Speedport 501 V
7. house
8. Vers. 4.0.10
9. T-Online
10. works
11. No other computers
12. New Problem
13. There is no blue world icon at all
14. I don't know and I tried to get help at the links I found on this forum but I'm afraid I don't understand what this all is about - sorry, stupid german who doesn't know to much about computers