can you use different cats and avivo codecs?

[KangooVanMan]

I've got a little problem with the new 7.8 cats. The avivo codecs no longer work, on starting the encoding a second later I get the CCC has encountered a problem blah blah blah and needs to close.
I was using the 7.6 cats before and it was all working ok (ish), but I heard that the 7.7's and up and improved functionality in the avivo pack, so thought it might solve the odd crash/strange behavior I used to get with the 7.6's.
I tried the 7.8 cats with the 7.6 avivo and it was the same (wasn't sure if it would work at all). Is it possible to use the 7.6 cats and the 7.8 avivo xcode? or is this asking for trouble? Or would I be better off using the 7.6 for both and putting up with the odd niggle?
Any thoughts?

 

[KangooVanMan]

I installed the 7.6 cats and 7.6 xcode again, and it's doing the same thing now
What on earth is going on?
I have noticed if I try and encode divx mpeg4 to whatever, I get the error message but the encoding does seem to continue if I don't press ok on the error box. If I try and encode .wmv files to anything it doesn't do a thing. I'm really puzzled.