Knytt Stories has started hanging when I save.

It just started doing this.  I'll press down to save, and the game will lock up for a couple seconds until it's done saving.  I downloaded a new copy and ran it from its own folder without any new levels, and it does the same thing.  What's going on?  How can I fix this?

I'm running 64-bit Windows 7, should that be relevant.  Again, I have not had this problem before now.

Nothing's changed in KS for a long time, so the problem must lie elsewhere.  I'd look and see what processes are running in the background (ctrl-shift-esc).  Something else could be accessing your hard drive so KS has to wait it's turn.  If you don't find any obvious culprits, you could try raising the priority for KS.  Right-click on it in task manager to raise the priority and save the new priority.

Raising the priority didn't help, but I realized that I'd had Firefox open for a few days (and I normally don't use it at all).  After a restart, the problem has disappeared, so that was probably it! 

Saving is only doing disk activities. So the only reason why saving can be slowed down, is because something else is reading/writing to the disk as well. (okay, not entirely true, bad sectors or other reasons why an entire harddisk slows down is another reason) Task manager does not just show you which processes consume the most processing time, but also which consume a lot of memory, and which do a lot of reading/writing to disk.

Next time this happens, check the task manager and sort for disk activity to find the troublemaker.

Yes it could've been firefox.