External monitor will not detect in T450

[edson_alvarenga]

Hi,

For many days I'm trying to use my new external LG 29UM68 monitor with my T450 notebook.

I want to use the Mini DisplayPort with HDMI, I have tried many different cables.

I'm using the follow Thinkpad Setup: Boot Display Device: Digital on ThinkPad and Total Graphics Memory: 512MB

When I turn on my laptop, I can see on the external monitor, the message asking to enter BIOS Setup. After that I can see the Symantec Encryption screen and when the windows start to load. I can see the progress indicator, after that, I can't see anymore. The external monitor shows the message "No Signal".

I open the laptop lid and I can see normal screen, but in Device Manager in Windows 7 doesn't show "LG Monitor". I already updated the drivers, BIOS.

This problem only occurs with Mini Displayport, when I plug another external monitor in VGA port, the monitor works normally.

Thank you,
Edson

Moderator edit: Moved thread from initially, incorrectly being posted in the T4x-forum.