There should be no conflicts running F-Secure and Malwarebytes Pro with real time scanning. Malwarebytes pretty much works with everything. But please keep this in mind: More is not always better when it comes to security products. One anti-virus suite (like F-Secure Internet Security 2013) plus Malwarebytes Pro should work just fine. But throw in a second real time anti-malware product like SuperAntispyware
and you may find the computer slowing down or having other issues.
Malwarebytes Pro offers a free 14 day fully functional trial. Use it and see what happens. If you don't have any problems you could always purchase the Pro version. If there are conflicts, just use the Malwarebytes free version. It does not have real time scanning and only operates as an on-demand scanner.
Malwarebytes : Start your trial of Malwarebytes Anti-Malware PRO now and start removing malware including viruses, spyware, worms and trojans