Interesting. Did you create the surface tin files with Carlson? If not, it's possible Carlson can't read the surface correctly.
Have you tried to run One Triangulation Surface Volumes and setting your datum arbitrarily low (or high)? If you set the reference elevation to 0.0, run the command and you still get no calculations then there is something wrong with your software installation. If it reports a volume, then you know the surface is good.
If you made the surfaces in Carlson (and you know they are good, ie you can build contours from them), then make sure you are using 2 unique surfaces. I just ran the command selecting the same surface for both Existing and Final and this is the report that was returned.
Volumes by Triangulation (Prisms) Tue May 11 11:53:28 2010
Existing Surface: S:\__Share\__2010 PROJECTS\054-835-B. 74 Pine Rd - Septic Design\DTM\054-835B Surface 5-10-2010.tin
Final Surface: S:\__Share\__2010 PROJECTS\054-835-B. 74 Pine Rd - Septic Design\DTM\054-835B Surface 5-10-2010.tin
Cut volume: 0.0 C.F., 0.00 C.Y.
Fill volume: 0.0 C.F., 0.00 C.Y.
Area in Cut : 0.0 S.F., 0.00 Acres
Area in Fill: 0.0 S.F., 0.00 Acres
Area exactly in daylight: 7,753.9 S.F., 0.18 Acres
Total inclusion area: 7,753.9 S.F., 0.18 Acres
Export Volume: 0.0 C.Y.
Elevation Change To Reach Balance: 0.000
Volume Change Per .1 ft: 28.7 C.Y.
Cut (C.Y.) / Area (acres): 0.00
Fill (C.Y.) / Area (acres): 0.00
If your report is giving you a Total Inclusion Area but no area calculations then you are using the same surfaces.
Alternatively, you can draw the two tin files on different layers in Carlson and use the "Volume by Layers" command under the surface menu.
Eric J. Morse, P.E.
MEC Industries, LLC