Today I'm very glad to download mIRC 6.15, and everything is OK on my computer (My OS is Windows XP Pro). But some people using windows 2000 said another multi-byte bug also exists! Whatever multi-byte support is enabled or disabled.
On their computers, if they join a channel which have a Chinese name, or open a query window whick have a Chinese nick, they cannot see the button on the switch bar, and from then on, the switch bar will stop repainting whatever open more English or Chinese query window.
please see fig 1 & 2.
(fig 1)
(fig 2)
If the swich bar have a background, the bug will happen just like fig 3.
(fig 3)
And, if some new messages come, the "red words" will appear but the icons also disappear. Please see fig 4.
(fig 4)
They told me the bug has existed for a long time in earlier version. I'm so sorry for finding it so late because it never happen on Windows XP.