I don't know much about tabulating the data in Arc, but if you are getting a 3-band RGB image from ENVI, then I would suggest you do not save the file from the Display (at least not as a color image).  I think your best bet is to use the ENVI Reader for ArcGIS (for 9.2) to import the ENVI file natively.  ArcGIS 9.3 has this functionality built-in so the add-on is not necessary.  When importing an ENVI file to Arc, you must give the file an extension of .dat or .img so that Arc will recognize it.  If it has any other extension, it will not read the file as 'ENVI' format.  Your next best option is to use File ->Save File As->GeoTIFF.  This will save the file as a single band TIFF (grayscale) but it will not retain the class colors.  You will have to reassign colors to the data values in Arc.  If you save the file from the display, ENVI will make a 3-band RGB image which loses its original class values.  While it will look the same, it will not be the same as a classification image.