If you have problems opening an '.sea' (self extracting archive) just replace the '.sea' extension with '.app'.
After I downloaded the last Espon 750 driver in '.hqx' format, Stuffit expanded the '.hqx' archive, then when I double clicked on the '.sea' file, stuffit launched and did nothing. So I hilighted the '.sea' archive, typed 'Command-i' and change the '.sea' extension to a '.app' extension. After all, an auto-extractible archive is a kind of application!
I then double clicked on the archive and it happily extracted itself.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20020307210124308