I've been having this problem for a number of days now. When I update the contents of a folder using terminal commands, by decompressing archives, or by using "Save As", the affected folder often fails to reflect these changes. Sometimes it takes quite a while for any files to be shown, even if the total size of the folder is fairly small (< 10 MB).
I'm running an '09 MacBook Pro 13", so it isn't the newest system, but it certainly has enough oomph to display a list of files in a folder. Does anyone know what might be causing this?