OK, so this is interesting:
Made a new cbo box on my form using the wizard. Set the format to "general number" since the column in the table it is referencing is set to "number"
All of my original 5-digit IDs all start with 10. If I start typing 10 and the next number is 0, 1, or 2, it continues with the predictive text to a point. It will accept 10115, but not 10123. It does the same thing with number starting 102. But eventually it will stop predicting if I get high enough, like it will accept 1022 but not 1023---. Numbers starting 103 and higher give me the error no matter what.
Could something be lurking in the table itself?