突然就不对了。
解决方案：
I had the same issue, after a few days of search found a fix that worked for me
WARNING: this WILL reset blend settings!
go to C:\Users\<user>\AppData\Local\Microsoft\Blend\15.0_c2edcfdc
and delete privateregistry.bin
launch blend, the 'setting things up' screen will appear, after its done (took ~30 secs for me). Blend setting will be reset,
But it would work as expected from this point on
参考：
https://developercommunity.visualstudio.com/content/problem/36026/blend-for-vs2017-crash-on-startup.html