I have faced this issue twice this week. (no vim plugin installed).
The keyboard suddenly stops working (both external and macbook pro). The mouse stays active and I can copy, paste, mark code and move it etc..
I have never noticed any circumstance that could lead to this but it was very annoying because I had to restart IntelliJ.
IntelliJ IDEA 2018.1.5 (Ultimate Edition)
Build #IU-181.5281.24, built on June 12, 2018
JRE: 1.8.0_152-release-1136-b39 x86_64
JVM: OpenJDK 64-Bit Server VM by JetBrains s.r.o
Macbook Pro i7 3,5GHz, 16GB Ram