Thanks for your bug report. I have not been able to reproduce this here so far. I tested your script, and the Options dialog Nickname section, on several different Windows installations. mIRC is using the EnableWindow() API, which is a basic API used to enable/disable controls. The way the control is re-drawn in this case is handled by Windows. This API is used in many places in mIRC, and has been for decades, and I have never heard of an issue with it before. I cannot think of a reason why this would happen, apart from perhaps a Windows graphics driver issue.
