If you are using both HG612 Modem Stats and DSLStats at the same time, is only one of them set to upload data to MDWS?
Also, have you set HG612 Modem Stats co-operation within DSLStats to ensure the programs don't clash?
It is possible that you have one or more 'stuck' instance of HG612_stats.exe.
It should appear in Task Manager for a few seconds every minute.
If it doesn't disappear after a few seconds, you could end the process in Task Manager, which should start harvesting & uploading of data again.
You could always post the last few every minute entries from the file named ONGOING_ERROR.LOG_file_ERROR.TXT for me to have a look at what might be going wrong.