DOS Informix - ISAM error number -24

I am currently in the process of porting an existing system from SCO XENIX to DOS under Informix 4GL V3.61. I have hit upon a problem where I receive the following error message :- Program error at cbak.4gl line 180 SQL statement error number -229 ISAM error number -24Could not open or create a temporary file. The line it stops at merely reads OPEN cu_due where 'cu_due' is a previously defined cursor. The problem occurs *ONLY* if I have previously issued a 'RUN' command to call a DOS batch file. The batch file is used to call WordPerfect 5.1, although calling a batch file that does nothing will then proceed to cause the above error. The problem does not occur under XENIX. I have read the manual, error number -229 tells me to look at the ISAM error, but I cannot find any trace of error -24! Can any one please help! Mark.