After running again and again into the basilisk next to Shattrath to get into combat and figuring out that your InCombatLockdown() doesn't work directly after PLAYER_REGEN_DISABLED, I got the solution
I've build it in your HBarHide-code:
http://www.pastey.net/89544-3f44:89543-j6gw
Shouldn't be to complicated to understand it, the Event()-function will be called if combat state changes and then the GameTooltip-lines will be cleared. At last we call the Enter()-function so that it will insert the appropriate text into the tooltip.
edit: one question - why do you toggle the bars with SetPoint() ? I have such a bar toggle button in my interface as well (but it's not as nice as yours
) and I use the Show() and Hide() functions. So if the user moves his bars with another addon, the toggle button would not interfere in positioning.