The PC's run fine for more than 3 years and I've never had this problem till now.
So, the entire 3 years and more, you had the computer for ... Was Windows 8.1 installed on it?
Also, is your Windows 8.1 with a official Microsoft license? Is Construct2 the free version or the Licensed Version? things might occur differently when software's are not the official latest release, but outdated ones.
Are you using the standalone Construct2 downloaded from official Scirra site or the Steam version? What Construct2 Version are you using?
The lockup thing didn't happened before, and from 3.5 millions downloads this is the first time i see this appearing in forum, im just curious about all elements, since all this elements matter into pinning down the mysterious problem.
If all the answers to the above questions are Right(meaning=you had windows 8.1 since it was released in 2014 on this computer u are using now and never C2 did this, every software is licensed on ur computer and its not a torrented version that might cause this problem, C2 is not the steam version since the problem it can be caused by the steam playtrough feature, Construct2 version is not older then R239 since that is the official stable release.) then i have no real response to fix your issue, but instead i suggest you file this problem into a report at the Bug's Section
If some or part of the software's you are using (windows/C2/other software you use in same time while you are working in C2) are not licensed or are from torrent downloads then i suggest get the official version of them, cause in that situation no one really can help with a official response, and you might be subject to sanctions for breaching licensing terms.
I'm not saying you are doing something wrong or illegal, just being thorough, so me or a more experience user in this matter(more experienced users, moderators, C2 creators) can provide you with a perfect response and fix this issue that might affect us all, as well the future updates and future users of the C2 product.
Hope you read all the above, also i hope if you found why is the problem with the lockup happening, to reply here or in the Bug's Section so the issue to be patched in the future updates. Thanks.