I've had a similar problem. I enter in my workout and it shows up with cals attached. When I come back to the page later, it's gone. I have no problem with the nutrition tracker. (FWIW, I've used spark off and on for about 5 years. This is the first time I've had problems).
I've totally given up tracking my workouts as a result.
edited to add: I'm using Google Chrome
Edited by: BLUESLEEP at: 6/14/2013 (11:54)