Custom function - report only runs under the creator's Windows logon

I've created a Crystal 10 report that produces a file which is exported as a text file with fixed length fields from within a third party application for which I don't have the source code.

To date all of the Crystal 10 reports I've created work fine in the application which uses Crystal 9 runtime files.

I used the custom function, below, in this report to pad string fields to the length I require. There is no built-in padding function in Crystal 10.

 Function (stringvar InString, numbervar StrLength)
 // PadExact - make a string field an exact length
 // Input: InString, the string to be trimmed or padded
 // StrLength, the desired length
 // Example: PadExact(City,10)+State
 // Antioch TN // Nashville TN
 // ChattanoogTN
left(trim(InString)+ space(StrLength),StrLength);

I can run the report from within the application on any PC on my network under my own Windows logon, but it returns an error under any other user's  Windows logon.
 
The error message is:
 
“The Report Engine was unable to run the report.
 Please check that all the Report Engine DLLs are
 present on your system”
 
The Report Engine DLLs are all in order on the PC of the user who needs the report.
 
I've tried installing Crystal 10 her PC. The report runs fine withinin Crystal but the error still appears when it's run within the application. The user has 'full control' permissions for the file.
 
Any advice would be appreciated.