I don't know if this is just a stupid thing to say - but I'll say it anyway, just in case.

If you have a whole lot of bookmarks your list may be longer than your computer screen. There's a down arrow at the very bottom of the list. If you put your cursor on the down arrow, (no "clicking" necessary, just place the cursor there) the list will roll upward allowing you to see all your bookmarks to the bottom of your list.

I've got at least 100 - 200 bookmarks and I have prevented this problem by creating folders and sub-folders to store my bookmarks in categories.

To add a bookmark to a new folder using Firefox 4

Click > "Bookmarks" > "Bookmark this Page". A window will pop up. Click the down-arrow in the "Bookmark Menu" box. Click > "Choose". Click > "New Folder". Type the name of the folder in the "New Folder" box. Click > "Done".

If you already have a folder made:

Click > "Bookmarks" > "Bookmark this Page". A window will pop up. Click the down-arrow in the box that says "Bookmark Menu". Click > "Choose". Click > on the folder you want the bookmark stored in. Click > "Done".

Thanks Robin. I don't have very many bookmarks. Just a handful, so I don't think this is the problem. I appreciate your answer though.