try moving some of your files into a new folder on your desktop and viewing them. I don't use ACDSee these days, but I seem to recall smaller folders keep things moving quicker. If things work fine on files in that new folder you may be wise to do some re-organizing of your files and folders; more folders with fewer files each, and not very many levels of subdirectories.
I use IrfanView now, but I'm not a big fan of it either.