The cause of the error is that the database is showing duplicate badge numbers when it tries to open that list, causing an error. Usually this is due to an employee having been removed, then a new employee given the same badge number.
Download and extract http://dl.waspbarcode.com/wasp/supportfiles/DuplicateBioscanTableEntry.zip on the server machine, then run Update.bat to correct the issue. The batch file will create a backup of the database in the default SQL backup folder (usually C:\Program Files\Microsoft SQL Server\MSSQL.1\MSSQL\Backup) with filename WaspTime_<date stamp>.bkp prior to making any changes in the database.
We have also seen an instance where there were 2 active employees with the same name and same badge number. This should not be allowed by the software, but if you find the same situation has occurred, determine which one has been receiving the current punches, and archive the other.
If the issue persists, there will be a DuplicateBioscanTableEntry.log file created in the same directory where you run update.bat. Please send me that file and let me know of any new errors.