I know that a lot of people is having the problem that when they enter live battles the game crashes and you get an error : M2TW encountered an unspecified error and will now exit. I had this problem and wow it was so frustrating. I finally found a wierd solution and I thought it was a joke but some people wrote in the comments that it worked so now I want to help ppl who is having this error!
You will probably laugh because this is rediculous. Go to "Change Time and Dates" then "Change Timezone" remove automaticly adjust clock for daylight saving changes" and boom my problem was solved! If this does not work then it must have been something else that I've done earlier or that you havnt done. I don't exactly know what or if it matters at all.