Cumulative backups with ASE 15.7 SP100

Hello,

I am trying to perform a cumulative dump on an ASE 15.7 SP100 server using a third-party library, but I am getting this error from the backup server when the dump cumulative command is issued:

Error from server SP100: Msg 8009, Level 16, State 1

        Error encountered by Backup Server.  Please refer to Backup Server messages for details.

Error from server SP100_BS: Msg 303502, Level 2, State 1

        Backup Server: 3.35.2.1: RPC bs_begin_phase refused following previous FAILURE return.

Error from server SP100: Msg 8006, Level 20, State 1

        ASE error detected by Backup Server. Refer to the preceding Backup Server message.

However, if I run the native isql command:

dump database abc cumulative to "abc.cml"
go

It runs fine.

Does anyone know what's going on here? I haven't found any reference to these particular error messages on the Sybase website.

Thanks in advance.