At what point does the error occur? I have found that the CPE app does data validation on the back end (after submission), but does not enforce the same rules in the UI (while entering data). You might try going to the page that caused the error and making all the data as "simple" as possible --- nothing too large, limit punctuation and avoid Unicode characters.
The one that bites me the most is a length limit on the "author/presenter" field. I have learned to strip out job titles when I copy/paste from a BrightTalk viewing certificate, which seems to keep it short enough.
And, when entering partial hours, try a period to separate the fractional hour, instead of a comma.
You might also try a "testing" entry that has the simplest possible data in each field to make sure the overall system works for you. Just be sure to delete it afterwards and to make it clear that it is testing data incase it gets hit by a random audit. E.g. you might make the title be "Testing that CPE submission works".
