Symptom: When opening a label file, this error is displayed: "Error Opening File: There was an error opening the file." After clicking OK on the error, the properties window will disappear, but the label appears to be correct, the data is shown on the Data tab, and you can print the label.

If you check the WaspLabelerV7.log file in C:\ProgramData\Wasp Barcode Technologies\Wasp Labeler V7\7.0.1.0, it will show this error:
ERROR       | Class: MainViewModel, Method: LoadDesign, Error Description: Specified argument was out of the range of valid values.
                   | Parameter name: index 

Cause: You have a filter created, but No Filter is set as Active. This causes the data to be indexed incorrectly.

Resolution: Either delete your unused filter(s), or highlight a filter and click Set As Active.