Environment: CR-2008 (version 12.6.0.1596) on a 64 bit Windows-7. Connected to ASE 15 through ODBC.

Recently, all of a sudden, the reports which read negative values from 'money' fields started to show huge negative numbers - obvious signs of overflow.
In the simplest case, the query for a constant:
   select M=convert(money,-1)
The M field in the report is shown as ($922,337,203,685,478.00).

This problem exhibited by several independent installations of CR so I started to suspect that some changes were done to the database server. But DBAs are insisting that no such changes were made to the database server, and I cannot find anything which can be responsible for this in the server documentation.

Does anyone know what is going on and how to fix it?

Just did the straight forward test: wrote a tiny program in C which connects through the very same DSN, runs the very same query.
The result - no error.
SQLDescribeCol() reported
name=M type=3 size=19 decimals=4 nullable=0
The SQLGetData returned "-1.000" in the SQL_C_CHAR buffer.
So the problem is not in the ODBC and not in the database server.

but why several Crystal Reports installed on several independent computers suddenly started to print garbage???

No idea what is going on.
but You have one field of money from database so try to do basic format object using some function of Crystal Report and also round of it

I'm not so sure but might be it will help you.