It shuts the installation down. And when i try to reboot with the diskette in, it runs for about 10 seconds and stops in Amigados with the number 1..
That sounds really bad... It seems like it somehow tried to install on the floppy instead of the HD, which means your WB floppy is now ruined.
Always keep your valuable floppies in write protection.
I hope you have backups?
That is also one thing you should do when it comes to disks like WB, make copies.
If you have no backup, then i suggest you upgrade to 3.1 while you are at, since it works just fine even with kickstart 3.0 and has quite a few improvements over wb 3.0.