bnwrx wrote:Stop Cumulus. Go to the backup file and use the backup file before the problem, using its data files to replace the current files. When I did this and restarted Cumulus, it loaded up the backup files and made a new entry for the 7th.

Yes, that's one way of solving it. You can also look in the diags file for mention of dayfile.txt and find:
5/8/2011 17:05:44.944 : === Day reset for 5/7/2011
5/8/2011 17:05:44.946 : Error writing dayfile.txt: I/O error 32
5/8/2011 17:05:44.946 : If the above error mentions I/O error 32, something on your system is locking the file and preventing Cumulus writing to it
5/8/2011 17:05:44.946 : Cumulus has been unable to write to dayfile.txt; please insert the following data into the file
5/8/2011 17:05:44.946 : 07/05/11,28.2,270,12:24,43.2,04:00,73.8,15:24,29.97,17:01,30.06,00:00,0.00,00:00,0.00,0.0,88.6,12.1,11:53,10,15:27,40,04:10,0.000,0.0,73.8,15:24,66.0,17:01,37.4,03:30,0.00,00:00,43.2,04:00,22.4,10:34,1.2,18:50