All of a sudden, Clients can not connect and B1 crashes

Hi

I had 9.1 PL10 running for about a month without issues.

After a new start of all servers, some clients can not connect anymore. Everything else works as usual on all clients and some clients can connect as usual. On the affected clients, the B1 logon screen appears and after entering the logon, B1 locks and need to be killed.

Reinstalling did not help.

Any ideas what can cause this and/or how to debug'

Thanks

Franz