Hi Tim,
Adobe CS 5 is a 64 bit application – Adobe CS 4 is a 32 bit application. The freebie BCC Mosaic and Tritone filters that you were using were designed to be used in a 32 bit application and cannot be used in a 64 bit application. There is no way to get them to work.
We recoded the filters in the BCC package so that they are 64 bit with the BCC 7 release, in an effort to make them compatible with 64 bit applications, such as CS5.
The only way for you to use these filters in CS 5 is to use the 64 bit versions, which are available as part of the BCC 7 filter package. You can download a free demo version here:
borisfx.com/downloads
Cheers,
Peter.