Hi aldim, I asked the main SPEAR developer about this, and he said that in ENVI 4.6 all of the different SPEAR Change Detection wizards were folded together into one master tool.  The band picking wasn't necessary for most of the options in that new wizard, so he replaced it with the warning message.  That way people who don't need to pick bands aren't forced to. The idea, I think, is that you can always add the wavelengths for the image into the header, and then you can use the wizard the way you want to without having to pick the bands.  To add wavelengths to image bands in ENVI, you right click on the image in the Available Bands List, and choose Edit Header.  In the resulting Header Info dialog, choose Edit Attributes > Wavelengths.  In the resulting dialog, you can enter the wavelengths for your bands. I hope this helps. Peg

Thank you very much for your time and the resulting clarification. Kind regards,  

Well, I think you still need the message, because for some of the change detection options it does require wavelengths in the header.  It's just that not all of the options require it.  So, if you're going to use the options that don't require wavelengths, then you don't need to edit the header.  But if you are planning to use one of the options that does, and your data didn't have wavelengths, then without the warning, the tool would just quit with no explanation.  That doesn't seem OK.