It's quite common for the SecurityCenter to momentarily flash red when updating. Most times it's unnoticeable because few people have it open whilst it is updating.
PUM stands for "Possibly Unwanted Modification" and is only a warning. However, if Malwarebytes produced it then you should be asking on their forum.
A Google search for pum.securitycenter just brought up an item on their forums as the first choice.
By the way there have been posted issues with the paid version (as against the free one) of Malwarebytes and SecurityCenter.
I just read the first result of google like you said and it seems that the someone mentioned that because I have something like McAfee, McAfee disables the Windows Security Center notification, since it has its own.
I forgot to mention that I was using the free version of Malwarebytes. But basically am I right to assume that because I have McAfee and it disabled the XP Notficiation, everything is actually fine and there is nothing wrong with my machine?
Yes, everything is fine.
I see, thank you. I will marked this as answered.