The reason for this issues is the data corruption. All the values in picklist should have corresponding values in the stringmap table. If there are records with picklist values for which there is no corresponding values in the string map table, then the generic error will be shown.
Try to clean up the data to correct this problem. The way to find out all these records is:
1. Go to Advanced find.
2. Select the entity for which this error occurs. (For Ex: Account).
3. Select the column which is of type "picklist".
4. Select the operator as "Does not Equal".
5. In the pop up for selecting the picklist values choose all the values.
6. Click on Find.