Basically yes, too many attributes usually result in a bad inventory error message from D2. I don't know the actual limit for mouse over display in D2, but it is approximately 44 lines of visible text -- including the blank lines between different type of attributes.

For Hero Editor V0.80, the maximum mouse over limit is 100 magic attributes.

For Hero Editor V0.82, the maximum mouse over limit is 200 magic attributes.

So, I guess you must be using Hero Editor V0.80, lol.