Your best option is to use a program like Acronis Disk Director/OS Selector and setup your partitions with the option of "hiding" the other OS from the one you are booting. This eliminates the chance of there being any conflicts because it is a possibility when two OS's see each other, especially similar OS's that there can be problems.
To illustrate my point you have:
and each is setup so that when you boot the one, the other will automatically be hidden, so:
From OS Selector screen, you select to boot OS 'A', the program will automatically hide OS 'B' and it's partition as if it didn't exist and then boot into OS 'A'. And of course vice versa.
I have this setup for my Win 7, XP, and Leopard.