They can be installed at the same time, but running both simultaneously probably requires very careful setup, and even so might not work. Was it ever supposed to work?
- they can't open the same library (except if they're in Client mode) due to read/write file locks
- they need to use different ports, they can't be both on 52199/52200
- they probably can't both be DLNA servers (same ports, again)
- single instance setting should probably be off in both
- If the code uses the same MUTEX names across versions, then it won't work at all or will freeze while doing some operations
