Could be a corrupted picture in that folder.
Things to try:
- Set to "detail" view. If that helps, and you don't mind not seeing thumbnails it's solved.
If not solved:
- Move all pics out and delete thumbs.db (hidden file), then gradually move pics in again until you find the culprit.
If it's just a question of too many files in it, start making subfolders and move pics into those.
I am running Windows 7 Home Premium 64bit and lately my Pictures folder is taking an age to open and frequently doesn't respond. Everything else seems to work fine and opens normally - it's just this one folder. I'd appreciate any suggestions!