Easiest immediate fix would be to reinstall Sonar.
but...
>this happened the other day
Not a good sign, program dlls do not normally self corrupt. When this kind of stuff happens more than once in a blue moon usually something is wrong, maybe very wrong .
- Be sure that your data is backed up.
- Check the integrity of your harddisk.
If not an SSD run a disk check on your system and have it scan all sectors. Etc.