From the Tech Geeks:

We suspect that the user’s experiencing problems might be seeing issues with their actual local browser cache, or perhaps a cache upstream that the ISP is using (some ISP’s still employ their own caches to save on their bandwidth bills)

The next time someone reports this, I would have them first try a different browser (to ensure clear cache). I would also have them try the force a refresh trick in Firefox. Have them hold down the shift key and hit the refresh button in the toolbar (or hold down shift and press the F5 key)

Have at it kids. Let me know if it helps.