I'm using DW CS3 on WinXP and am recently having the same problem. Find and
Replace has become unreliable. It finds some code to replace, but ignores most
of the files. I now have to open each file manually and search it.

I don't know how if this is related, but Dreamweaver seems as if it does not
recognize that the local folder where all my files are is the web site. I can
no longer reliably sync the remote site. I have to put each file individually.
In other words it often ignores the fact that older files are on the published
website, but it ignores some, warns about others, and syncs a few. I end up
with a mess of broken links.