It may have something to do with the north orientation in carlson. It has been a long time since I have used 2007 but if I am not mistaken it uses a basis for angles starting at East(or the x axis) and then adds 90 degrees to that to make north (or the X axis)the basis for angles. It goes back to Autocadd. AutoCADD was created for Architects and used the basic xy axis. Using x as zero angle and measuring angles counterclockwise. Then surveyors cam along and wanted 0 or north to be up the screen and angles read clockwise.
Long story short I think when the Mtext edit dialog is open there is an angle setting that tells the text to rotate 90 to the x axis and not the y. I think you can add 90 degrees to this and it fixes it(or -90). It is a glitch that does not happen much but will forever haunt that particular drawing.
Hope this helps