I bought new Lenova Yogapad Pro with Windows 8.1 and installed Thunderbird and Firefox on it. Both Mozilla applications will start to increase in memory usage in very short time period. Thunderbird starts with 80Mb but when it has been opened for one full working day then it eats up to 3.2GB and then eventually will crash or I will close it since it is too slow or not responding when browsing emails. Firebird acts the same. Starts up with 160Mb and starts to increase memory usage even with just one tab with Google Calendar open. In less than one minute it has doubled to 330Mb and will increse by each second up to 2.5Gb. Then I it will crash or hung. So I need to close and open them both constantly which is very annoying. I have no problem with using them on my other machine running Windows 7.