Apparently, it's corrupted. To be sure, compare the size (with what's reasonable for such a document) or use a hex-editor to see what it really contains and compare that with a real undamaged word-document.
If you don't have a backup, I'm afraid nothing can be done about it. Are you sure you always use the 'safely remove hardware' method to remove the flash-drive?
I had created a Word (.doc) file on my laptop with OpenOffice Writer (Save As > Word), and copied it on to a flash drive. Since I accidentally deleted the original file on my laptop, I thought I would simply copy the flash drive version back onto my hard drive and use it.
However, this file can't be opened. When I click on it, a "File conversion" dialog box. Whatever I do, the two or three-page document opens with 1,084 pages of garbage - mostly special characters. Meanwhile, other Word files - those created in Word on other computers, as well as those created in OpenOfice Writer on my laptop - continue to open correctly on the laptop.
I searched the forums and found that others have also faced similar issues, but could not find any definitive solution.
I would really appreciate some help with this problem.