Try this, to recover your bookmarks:
Set windows to show hidden files,How to see hidden files in Windows
Then navigate to:
C:\ Documents and Settings \ "your user name"
\ Application Data \ Mozilla \ Firefox \ Profiles \ random characters
See if you have a file in there named bookmarks.html
That's your bookmarks.
If it's in there, it's possible it has become corrupted.
Right click it, and select Delete
, then proceed to the next step.
If it's not in there, proceed to the next step.
Now, open the file called bookmarkbackups
Locate the file with the most recent date.
Right click it, and select Copy
Click the Back
button, closing the bookmarkbackups
Now, right click on an empty area in the open window, and select Paste
Right-click the file you just Pasted, and Rename it to bookmarks.html
This will put a copy of the most recent backup, in your Profile folder.
Close the Profile folder.
Re-start Firefox, and see if you have your bookmarks.