TDS, RPC malformed packets with SQL Server 2005

Hello,

we have a standard apappliaction which uses a sql server.
Till last week we use a sql server 2000 and no problems.

Now we use SQL Server 2005 and now we got 40% malformed Packets in
application traffic to SQL Server.

Wireshark means TDS, RPC malformed packets.
If the session crash the application crashs also.
I have tested with two different Clients and two Hardware different
SQL Servers.
Both SQL Server has the same problem.

We use:
SQL Server: Win 2003 R2 engl., SQL Server 2005 SP2 engl.
Client: Win2000/ Win2003 engl.
NW Lib: Native Client with TCP/IP (no Shared Memory, no NWlink)

Does someone has an idea what i can test or what i can do?


greetings
Henrik