I had this same problem last year. I believe that your ExpressScribe is corrupted and it is creating problems also for your dss files. I would start with uninstalling it and cleaning your registry to remove all traces of it from your computer, also delete your download file. Then I would redownload it and reinstall it from the beginning. See if that helps. We got to the point where we made an image of our computer from the point right after we had formatted the hard drive and had our operating system and all major programs installed on it but had not yet used the system. This way if I ever had a problem I could simply reinstall the image (after backing up any files onto separate media) and have my computer fresh from the start. I hope this helps.
As a side note, I use Transcription Buddy, but it does not read dss files, so I have to convert my files. I convert to .wav format because I don't have any problems, whereas with converting to .wma files I sometimes had problems.
Good luck