I've had a small issue with most all of my Melda plugins since I've had them and it's been bothering me. Basically what happens is that the moment I load a Melda plugin the sidechain input meters are pushed to maximum as shown below. I contacted Melda and an excerpt from their response is below. Upon receiving the response I've done some testing. Basically when I load a Melda plugin and the problem occurs then I simply select a sidechain source, change processing from L+R to anything else (L for example), switch the sidechain input off again, and then select L+R processing. The problem then dissapears (but reoccurs the next time).
Oh and just discovered: if I "resolve" the problem as described above then it returns all by its self even if Mixcraft is just left standing on its own for a while i.e. after getting the meters to .inf they shoot up again on their own as if by magic (just happened to me while I was posting an another thread around here).
The Side meter is actually not related to Mid/Side processing, it's a level meter for sidechain and apparently Mixcraft doesn't really initialize sidechain input unless you send something to it.