I am getting Preview could not be loaded after initialization. LRT 3.4.1, Windows 7 64 bit.
2015-01-21 22:20:56] DEBUG: ExifTool output: 38 image files read
[2015-01-21 22:20:57] DEBUG: ExifTool output: 40 image files read
[2015-01-21 22:20:59] DEBUG: ExifTool output: 40 image files read
[2015-01-21 22:21:00] DEBUG: ExifTool output: 40 image files read
[2015-01-21 22:21:01] DEBUG: ExifTool output: 40 image files read
[2015-01-21 22:21:02] DEBUG: ExifTool output: 40 image files read
[2015-01-21 22:21:03] DEBUG: ExifTool output: 40 image files read
[2015-01-21 22:21:04] DEBUG: ExifTool output: 40 image files read
[2015-01-21 22:21:05] DEBUG: ExifTool output: 40 image files read
[2015-01-21 22:21:06] DEBUG: ExifTool output: 10 image files read
[2015-01-21 22:21:06] DEBUG: Timestamp Data complete!
[2015-01-21 22:21:06] DEBUG: Loading preview with ExifTool: CRW_1102.DNG... preview not available, trying to load embedded jpg... could not read embedded jpg either.
[2015-01-21 22:21:06] ERROR: Could not load DNG preview, probably there is no one embedded..

>> Could not load DNG preview, probably there is no one embedded..

Most likely the problem is that the DNGs don't have previews embedded. Which camera was this?

You can open the sequence in Lightroom and choose "Metadata/Update DNG Previews and Metadata", this will create the DNG previews. Make sure to not having edited anything in the sequence before.

You are right DNGs didn't have previews embedded. This is a Canon point and shoot with CHDK hack. It happened CHDK doesn't put a preview into DNG.
Thanks.