This is more a database problem than a shell one, but we have a problem affecting our scripts, so I'm stretching the limits a bit! 
We're in the process of migrating our application and a large number of associated scripts from Sybase 12.5.4 to Sybase 15. Scripts using 'isql' and 'bcp' include the -X option that ensures that database passwords are sent encrypted. This works without an issue between a Sybase 12 client and server, and also with no problem between a S12 client and S15 server, and also it seems between an S15 client and S12 server. However, we get a failure to connect when using S15 at both ends. Removing the -X option sorts our problem.
So what I'd like to understand is what's going on with S15 both ends, and why the -X option is causing a failure