I went back to a previous version of UltraEdit and there were no issues. I returned to 18.104.22.168 and experimented, found that by removing "Show auto-complete dialog automatically" I was able to solve the issue on my copy. Go to UltraEdit -> Editor, Auto-Complete, then clear the Auto-Complete. This seems to have resolved the issue, so this is actually a bug or compatibility issue with 22.214.171.124. I'll post back if the behavior returns.