8GB Sandisk SDHC card unreadable on cellphone & computer

I am having this same problem and have tried to read the card on a compatible computer using the adapter.  I was able to use the card both with the phone and adapter before and now nothing is happening.  No one has posted a real solution to this problem.  I did not improperly unmount or remove the card prior to it having problems.  Other microsd cards work on both the phone and computer with no problem.  I too do not want to loose my data but it seems that there is no choice and the card is done. 

Several people have posted similar complaints this winter.  Could the problem be cause by the cold?  Everything was fine until I went out during the coldest day of winter so far.  Can someone post a real solution or explination and start with the problem being with the card and not with the user? 

My phone is an HTC Evo Shift.  The 8gb microsdhc card was purchased and installed at the same time as the phone.  I was able to read the card on the phone and computer, through both the phone as a usb device and through the adapter, with no problem for several months until this past Saturday.  I have reformated the phone.  The card can’t be read on any operating system, so I can’t even reformat. 

Is there a batch of defective cards out there?  Is there a virus or other malware destroying cards?  I have had the card for about 4 months, it is hard to believe that the card can be corrupted that easily or quickly.  There must be an explination.