Dragging and dropping the .sit file with the wrong file type/creator onto the Stuffit Expander icon usually does the trick for me. The problem I usually have is when archives get "cooked", or were downloaded in the wrong transfer mode. Things like 7-bit ASCII instead of binary for SIT and MacBinary II files. I have run across servers that force browsers to download BinHex files as binary, which doesn't end well either. Back in the old days, I would avoid this problem by downloading via FTP, but that option is no longer available in many cases. Now I have to rely on buggy web browsers and people who don't set the MIME types correctly on their web server.