[Touch Diamond, MDA Compact IV ROM Development] bill48105:
More info would be helpful as to your scenario. What did you try? What was it doing exact? Was the screen turning off right away after call was connected or like 5 seconds or 10 seconds or..? Was it for outgoing or incoming call? Was it light in the room & how bright? Was the phone in your hand or on a table when you tested? Was it plugged into wall or computer with USB? Was the stylus out? Are there any programs installed? Any of those things can affect if the screen dims or if it goes to sleep which turns off the screen..

Anyway, I did a clear storage to make sure nothing I had installed had made any changes. I am using Dutty's v4 MSVC rom. I did a test call out holding it in my hand in a day lit room and my screen did not go out.. Same holding the phone under my desk & laying flat on the desk. Maybe you installed something that changed some setting. I imagine even if you uninstalled it there could still be remnants. So doing a hard reset clear storage should fix it unless something in your scenario is different than mine.

Next I installed TouchLockPro 2.0, waited the 30 seconds after it installs to activate & did a test call. The screen goes black almost immediately after connecting. AH HA! TLP must be the culprit. I went into TLP settings & unchecked 'ScreenOffWhenConnected' (kind of obvious option..) on 2nd settings page. Arrowed right til the end & clicked upper right button to close TLP config. Did a test call & VOILA! Screen stays on! Do you have TLP installed or did you before?

Now it possible you didn't use TLP or maybe you did & removed it & some settings got changed so I decided to go old-school & check some registry settings since registry editor is included with the rom & some settings could easily be out of wack from defaults. As per the 3st link I sent you I used the built in registry editor & changed:

HKEY_Local_Machine\Drivers\BuiltIn\RIL\EnableFastDormantDisplayDuringCall from 1 to 0

I also changed:

HKEY_Local_Machine\Drivers\BuiltIn\RIL\FastDormancyRule from 1 to 0

I clicked EXIT to close the registry editor & used the built in reset app to restart.

The screen still stays on for me during a test call out in the same setting as stated above.

I decided what the heck I'll go all out & make sure this screen does not turn off no matter what & use Advanced Configuration Tool http://xdaforums.com/showthread.php?t=418151 to turn off that pesky light sensor polling just in case that might kick in. (I think Diamond Tweak can change the same settings but I already had ACT so I went with that.) I opened it & went to light sensor to find Light Sensor Polling already disabled. I see a Light sensor threshold to turn screen off set to 5. For kicks I turn on polling & restart when it asks. After it come back up I did a test call & screen went out after about 5 seconds once the call connected. I went back into Advanced Config and turned the light sensor polling back off, restarted & did a test call to find screen stayed on.

For kicks I figured I'd check other settings on Advanced Config. Under Phone I found "Phone sleep during call" enabled so I disabled it. "Fast sleep during call" was still disabled from when I changed the registry key. I saved & restarted & screen stayed on during the call.

Of course any of these settings could very likely drain your battery quickly but any could be the cause of your screen turning off & if you want your screen on badly enough I suppose you'll live with shorter battery life. ;)

Anyway as you can see there are so many possibilities of what is causing your screen to go out but one or more of the above should help you figure it out otherwise you might backup your phone & do a hard reset / clear storage & start from fresh.

Hope that helps solve the problem or at least point you in the right direction.

Bill