Nandu:
I didn't face a situation like this :(
Once I have a similar problem, but the issue was that the data class was created in another folder. Have you tried to search in the Altiris console, for that data class?
In the Altiris 6.5 console, there is a "row" on the top of the page, in which you can see the Altiris logo, the text "altiris console" on the left part. In the middle, there is information about the name of the Altiris server, and the credentials logged in on the console, and at the right, there is a edit box in which you can type any object you need to find in the Altiris server. This row is just on top of the Altiris menu. Type the name of the data class you are looking for, and press Intro. If it is in the system, it will appear in the "search results window". Double click over the data class, and the console will show you in which folder the data class is saved.
If it doesn't appear, may be you have the table created, but not the "data class" itself. In this case, I would suggest to delete the table and create the data class again from scratch.
Let me know if this helps you :)
Falquian