This version seemed perfectly fine with windows 7 x64 when I was using it, but then once I did a clean install of windows 8.1 x64, the program has some weird issues.
When I intentionally disable my current internet connection (disable through adapter panel), mIRC understandably dc's from all channels (I'm typically connected to 9 different servers at once), however on reconnect a percentage of the time mIRC just borks, and says mIRC has encountered and error, and windows tries to look for a solution. Sometimes this is a straight crash to the desktop.
Other times, when my internet hiccups on the modem end, the program has similar effects to what was previously stated.
Other times, perhaps from length of concurrent use (days) and being connected to many servers, the program just randomly crashes and windows tells me the program needs to close because it encountered an error.
Not sure what to provide to help facilitate fixes of these, they're somewhat annoying.