> We recompiled the procedures using IBExpert. It still fails with the
> same error message. Any other suggestions?

This error means that you changed input or output parameters in some procedure
but another procedure (which calls changed one) was not recompiled after and have wrong
references in its BLR.

In your case "bad" procedure expected to receive (or tried to send) message of 32 bytes
but real length of all output (input) params is 36 bytes. I.e. you added some params or extend
type of some of them (for ex. int -> bigint, varchar(n) -> varchar(n+4)). To resolve the issue all
you need is to recompile "bad" procedure.

Suggestion - look better ;) It is not necessary the procedure which client called - it may be
any procedure called or trigger fired during execution of top-level procedure\statement.

Regards,
Vlad

PS IBE have ability to recompile all procedures\triggers