I have Win7 64 and am using Malwarebytes and Bitdefender (quite happily) - both configured to ignore each other so no conflict.
I use Macrium Reflect as backup software - version 6 works fine with everything. Version 7.1 just installed - now BD will not start (no error, just does not appear). Trying to enable Protection from UI is not possible (error from BD). Have contacted Macrium - they suggest it may be because version 7 of their software uses a Guardian feature that may not work well with BD. Any suggestions as to how to keep using BD? Would you work with them to figure out a fix? I have a ticket number if so...