Number: 6, Description: Overflow, Module: Vote, Procedure: Main, Line:530
This error shows that the slide ID generate by PowerPoint is too long. The ID is not the same as a slide number. ID's are normally 3 digits.
To find the ID go to Help > Slide info
You will details like this if the ID is long.
It should be something like this.
What is the fix?
Unfortunately you cannot change the ID. It is generated by Microsoft, so you will need to create your voting slide again. First see whether you have a working copy in another presentation that you can paste in.
Alternatively, upgrade your ppvote software. Versions up to 5.1.3 do not allow long ID's. Versions from 5.2.0 and onwards do.