Hi,
Some conflicts are from programming errors, or sometimes two plugins are just incompatible.
The current version of MapPress is stable and I’m not aware of it breaking any other plugins. As for Event Calendar breaking MapPress – I can’t guess why, but an explanation about what doesn’t work and a sample URL would help.
My time for troubleshooting other plugins is limited, but if you’d like to also send a login to a demo site where I can see the issue and make modifications, I’ll take a look.