I did some testing with Integration Manager 11 to see if I could reproduce the error. I was using the Customer integration and had the following script working without problem;
I tried different scripts in slightly different formats and complexity and determined that the error occurred if the script looked like this;
The error message appears if the script has a blank line at the top; blank lines anywhere else in the script are fine and do not produce the error when trying to get back into the VB Script Editor.
The downside of this error is that once you receive it the only way to get past it is to change the field to not use VB Script and then back again; which does of course delete the VB Script attached to the field.