When I was at start of my update period I copied and pasted the original contents of the 4gb Sandisk SD card in it's card reader to a new  folder on my Virus and spyware free PC , then copied and pasted the contents of the folder to a new 16 GB Sandisk Class 3 SD card and did all the updating to the new larger 16gb Sandisk SD card and saved the original 4GB SD card. About a month before my update period expired, I again copied and pasted the software from the 16GB class 3 SD card to a new folder then copied and pasted contents of new folder to  a new 16gb Sandisk Class 4 SD card that I presently use in my now expired DS 708. I figure I could always try one of the older software cards I saved as backup insurance if I start experiencing a problem like you have, because if the issue isn't resolved with another known good working software card, who wants to buy a new update subscription just to find out you have a hardware issue besides, and the extra money could have been better spent on an upgrade rather than a update costs , months of scanner downtime dealing with near non existent support, another $300  and shipping head  to China and eventually getting a total care replacement new (refurbished?)scanner head (if it is deemed the DS708 problem is not because of your fault).
   Being in your shoes the first thing in order is make sure your PC is not infected with a Viruses or adware as well as anything infecting the SD card of your MaxiDas