HD has dramatically gone down?

[geriness]

Last night my hd was at 122.7 GB, and I left my macbook on overnight to let the maintenance programs run, as I heard that it runs between 3 and 5 am. This morning, my hd space was at 119 GB, so I tried erasing free space in dick utility, and then the hd space all of a sudden started going down, a little bit at a time. So I restarted my computer, and its now at 109.69 GB.

What happened? And how do I fix it?

 

[Tallest Skil]

Possibly a runaway log file. Download GrandPerspective and see if there is a file grossly larger than the rest (on the order of gigabytes). If it's a log, you don't need it and can delete it.