Cinepak doesn't come with AlamDV.
Cinepak is a very old and inferior codec, and is not designed to be used while editing. It was only ever intended to be used for internet distribution of the finished movie - although there are far better alternatives now.
Whilst editing, you absolutely need to use a 'lossless' type of codec, otherwise you will lose an awful lot of information each time you recompress the movie. Use either a DV codec or simply keep the movie file 'uncompressed'.
Whatever you do, don't use Cinepak, as that is the cause of your problems.