I've seen this before. The problem is not in your code but in your name mapping. Make sure that there are no child objects on that table that have the name of simply "cell". If so, rename them... You can simply add a number to the end.
The reason for the error is that TestComplete gets confused between the mapped cell and the Cell object you're calling in code. Renaming the mapped object is the best solution.
Why automate? I do automated testing because there's only so much a human being can do and remain healthy. Sleep is a requirement. So, while people sleep, automation that I create does what I've described above in order to make sure that nothing gets past the final defense of the testing group. I love good food, good books, good friends, and good fun.