First: My mistake, I am using a v130! I'm unsure if the failure occurs while the PLC is writing to the SD card, or if the act of reading from the SD card over Ethernet to my computer (Using SD Explorer) is causing the problem. Either way, I only discover something is wrong when I try and access the SD card via my PC. Also an interesting thing I have seen that I forgot to mention, is sometimes folders will disappear. When I originally format the SD card using the Card Manager, the Excel folder is filled with folders Excel 1, Excel 2, Excel 3, and Excel 4. Sometimes when I got online with the card in Explorer, 1 or 2 of these folders are missing.
Another symptom is duplicate named files showing in the directory. I cannot delete edit or move these, and the only way to fix is to reformat.
I am only writing CSV files to the root Excel folder and no other transactions are occurring. I am not emailing any data either. My PLC OS version is 3.006.14 (Jul 9 2012) with the T38 option.