I've my theory on this issue, as I've been able to replicate it on my HDTV, but I fixed it (sadly the fix can't be applied for ACD 24", you'll see why).
Tests conducted:
- MBP connected to HDTV through Mini DP <-> DVI <-> HDMI adapter (yes first Mini DP - DVI adapter and another DVI to HDMI adapter on it) and a low end quality cable (max bandwidth probably of 4.8 or 6.4Gbits/sec. Don't know the versions of HDMI this cable supports, but for sure it's less than 1.3)
=> NO issue at all
- MBP connected to HDTV through Mini DP to HDMI adapter (with sound) and a low end quality cable (max bandwidth probably of 4.8 or 6.4Gbits/sec. Don't know the versions of HDMI this cable supports, but for sure it's less than 1.3)
=>I had the issue with similar frequency than with ACD 24"
- MBP connected to HDTV using the same Mini DP to HDMI adapter (with sound) and a HDMI 1.3 cable capable of 10.2 Gbits/sec bandwidth
=> NO issue at all!
So my theory is that the issue comes from the computer not setting the right settings for the output signal and sometime use a higher transfer rate than the one supported by the cable or screen, that makes the screen to malfunction (cause of incompatibility with the signal it receives).
This explains why the problem doesn't appears when using DVI or VGA, as there are no multiple max bandwidth in that case, VGA is analogic (so talking of bandwidth in that case is a nonsense 😉 ), and DVI have only one max 3.96Gbits bandwidth for single link version and a variable max bandwidth for dual link DVI. Btw, did you remember the issues with dual link Mini DP <-> DVI adapter at the beginning? It was probably the same issue, as max bandwidth is not fixed, but negotiated, in dual link DVI, as for HDMI and DisplayPort.
Also I'd not be surprised if with some HDTV the problems persist even when using HDMI 1.3 cable, if those TVs don't support HDMI 1.3 themselves.
The good news: It's probably a pure software driver (or firmware) issue, not detecting correctly the right settings to apply for the output signal when used with native DisplayPort or HDMI.
The bad news: While it's fixable right now for HDMI screens (at least those supporting HDMI 1.3), it's not easily fixable for the ACD 24" for now.
Well in fact there is a fix that can be used right now, but it's expensive, as it requires to buy a converter like this:
http://www.atlona.com/Atlona-DVI-to-Mini-DisplayPort-Converter-p-17859.html, additionally to the Mini DP to DVI adapter. This solution have already been reported as fixing the problem by someone here, but it's an expensive solution, even though it gives the additional advantage to be able to use the ACD 24" with devices without Mini DisplayPort connector.
