Yes, it is possible to use RadToolTip with RadGrid "Classic".
There is one problem with it - when the RadGrid's own built-in AJAX is used to update the grid content area. The AJAX methods do not "inform" the rest of the page (e.g. the tooltip manager) that partial update occured, so the tooltip manager does not "know" that it should re-tooltipify the grid.
However, the problem is easily worked around by setting the RadGrid EnableAJAX = "false"
, and wrapping the grid into an UpdatePanel.
In case you are not able to get your project running, please open a support ticket and send us your project. We will examine it and make corrections so that it compiles properly.
the Telerik team