Why do I get a 1720 error when my InstallShield setup tries to run my VBS custom action? - vbscript

Question

The Custom Action is configured as follows:
Custom Action Name: MyCustomAction
VBScript Filename: <PathVar01>\MyFolder\MyVBSfile.vbs
ScriptFunction: MyFunction
Return Processing: Synchronous (Check exit code)
In-Script Execution: Immediate Execution
It is being executed via the following InstallScript code:
result = MsiDoAction(ISMSI_HANDLE,"MyCustomAction");
When the setup reaches that line in InstallScript, the installer shows an error alert, stating:
"Error 1720.There is a problem with
this Windows Installer package. A
script required for this install to
complete could not be run. Contact
your support personnel or package
vendor."
The result code returned by MsiDoAction is that of '1603', which, according to winerror.h, is:
//
// MessageId: ERROR_INSTALL_FAILURE
//
// MessageText:
//
// Fatal error during installation.
//
#define ERROR_INSTALL_FAILURE 1603L
Why is this happening? I was starting to doubt that the file was included properly. Yet, I am pointing to the correct file, and I've tried including the VBS via the InstallShield Support Files, thinking this would ensure the file was present with the setup, but same result.

Answer 1

Running the setup with logging enabled revealed the problem:
Action 13:29:19: MyCustomAction.
Action start 13:29:19: MyCustomAction.
Error 1720.There is a problem with
this Windows Installer package. A
script required for this install to
complete could not be run. Contact
your support personnel or package
vendor. Custom action MyCustomAction
script error -2146827278, Microsoft
VBScript compilation error: Expected
identifier Line 163, Column 37,
blnExample,)
To run a setup with logging enabled:
"C:\SetupFolder\setup.exe" /V"/l*v
c:\Install.log"
This forum thread was helpful.