When you say DTE do you mean the Deep Texture Editor you make bryce textures or do you mean import texture into Bryce as a psd or jpg file? If you are Having Trouble with the Deep Texture Editor that makes the Bryce only made textures What I would do is Unistall Bryce Completely from your computer(Back Up your work first particualary if the are in the create section you can do this by click on the object and saving as a .obp file. if it is the 2d images then I have one question do you like me use Apple Mac? Because there is no point doing so in Bryce 7.1 Pro as the images will come up blue and then crash(Bryce is not as good on mac anymore.) But from what you are saying it sounds like the Deep Texture Editor Type problem So Maybe the problem what you may need to do is once you have the two textures in Bryce together save them as a .matt file and use them that way also if this doesn't work Try reinstalling Bryce. 

I am sorry I can't be of more use Good Luck. 

Karl