That's a very old wallet even for Multibit Classic users. Last stable version is 0.5.19 for Multibit Classic. Its strongly advised that you upgrade to Multibit HD which is supported by the Keepkey hardware wallet team. Since you are saying that you did this transaction by yourself I am assuming your PC is safe but just for the case what OS are you using, Windows OS-es tend to bring a lot of unexpected things during their use that's why its good if you can switch to Linux. Multibit Classic, Multibit HD and Electrum both work very well under Linux and I am a proud user of them all. My advise is to upgrade to Multibit HD and move funds there or to Electrum as is practically the same thing.