Long boot time sinse deleting free space on macbook air

OSX 10.6.6
Macbook Air

I recently used the "delete free space" feature in disk utility to overwrite all my free space to protect deleted files (i don't know why). But sinse doing so my macbook takes considerably longer to boot up. Before deleting the free space it would boot in around 15 seconds, now it takes over a minute and on the blue loading screen i get the wait wheel, which never appeared before.

Does anyone know why this may be and, more importantly, how to fix it?

Is this one of the new Macbook Airs?
I would think if it is, that it has something to do with the way SSDs/Flash drives handle (mishandles) deleted items, and I assume someone will chime in on this shortly.

It's an older MBA, but it does have an SSD.

From googling i have seen a few people are having issues after running the delete free space utility, all of them have solid state drives. Boot time and shut down times are increased significantly.

I read somewhere that booting from the recovery disk and running delete free space again resolves the issue. Guess ill have to stump up for a superdrive now.