Brushes Question

I opened my photo shop today (I use CS4) and all my downloaded brushes were gone.  The only ones that were left were the defaults.  This has never happened to me before.  I've looked in the memories, but I didn't see anything under the brushes or the program errors like this. 

I tried reloading the brushes, but there was only one set in the load brushes option.  Is there some place else they might be?  I really don't want to have to re-download  all the brushes, especially as I I've noticed that some of the brushes packs that I had are no longer available.

THank you for any help you might be able to give.