SOLVED: Weird MP3 encoding issue...

For some reason, and ONLY on some tracks, the Sonar MP3 encoder creates a double length MP3 file?
 
Example, one song is listed in Sonar as running 3.56.10, but after encoding it lists in say, Windows Media Player as having a length of near 8 minutes, and after doing a physical timing it RUNS for 8 minutes too, so it does not seem to be a tagging issue.
 
Does anyone have any ideas on this? As I said it is not all files, seems to be random (although I doubt it as there must be a common denominator in the files affected - I just cannot find it 
 
Thanks
 
Oh, I am encoding all files at 41/16bit and using VBR "Best" option.
Further, I just did a test and exported as a straight Broadcast Wav - file result was exactly as is should be. It matched the length stated in Sonar, so it is something to do with the encoder, but it is only on the "odd" file here and there so I am really scratching my head here....I also tried re-encoding the same file to a new MP3, same issue.
 
EDIT: Seems it is a known issue using the VBR codec, in that it sometimes does not create the correct header/tag info. I used a little app called MP3 Diags which repaired the header info. All good now and the files are showing as correct length