Backup of my Portable Apps USB key

Hello,

I got Portable Apps 1.1 installed on a 4GB USB key with lots of data. I make a weekly backup of the whole key.
Since my last backup, I cannot more open/use any programm on the key!
Ichecked the backup. There also the programs are lost.

In the backup as well as on the key, the folder ..\ThunderbirdPortable\..\profile\Mail\mail.eco-rah.be is still there but the files are empty. Also the total amount of space used on my key is drastically reduced.
The other data folder are well backuped and usable.

I checked for the backups of the last weeks, and unfortunately have to notice that the problem appeared for the last 3 backups!

The pitty, all my Thunderbird mails and data for the last 3 weeks are lost!

Any advice before I reformat the key and re-install all the stuff?
I would be very glad if I could win back my mails and contacts.

Thanks for a reply

Sébastien