Import Favorites – Problem

When I am importing a previously-exported favorites file, somehow, someway, I am losing some of the sites bookmarked. Now, I am exporting/importing a file containing upwards of 1,200 favorites – is this part of the problem? Should I reduce the size of my favorite folder? I’ve tried this process several times, and each time, I am losing a few dozen favorites. It’s very frustrating. What can I do to fix this? Thank-you for your help. I am running on Windows XP.