This has happened to me twice with HL1, but was not reproducible on restart of the game.
Edit: I am running HL1 at 1920x1080.
Oh, derp. Yeah. I thought I had seen one, but didn't find it. I'll close here and comment there.
Thanks.
Nothing extracted yet.
System info: https://gist.github.com/385f8ecd3425deeecd9f
I encountered this while playing Dynamite Jack. I shift-tabbed to go into the overlay to check a message I was sent. I made a typo, and attempted to delete the extra letter I typed. This didn't work. I attempted to go to the space before the character and use delete but this failed as well. I attempted both after highlighting the letter, but to no avail.
It may be the fact that I'm playing at a low resolution (due to my netbook).
The only work around I've managed is highlighting multiple letters and replacing them with the necessary ones.