World corrupted (the bad kind)

I was recently playing a game of terraria on my computer
when i decided that it was enough for the day, i saved exited and left.

Now when i tried to acces my character again, the name was coloured red.
I was unable to click my character. I made a seperate character and tried to
load my normal world which caused my computer to crash.
This has happened to me twice before, can anyone help me with how I can
stop this from happening and how to acces my lost world(s)?