I am testing your product with all the other 3rd party software we use and we ant to make sure its compatible.
I am seeing a lot of problems with ajax and this tooltip,
the latest is PageRequestManagerParserERrorException when i enable ASPRedirectory from intesoft (http://www.intesoft.net/Home/
my tooltip was working until i added the asp redirector
i even put the radtooltip inside a asp:Update panel, same result.
my radtooltip are loaded using the onajaxupdate event.
I am unable to send a project attachment at this point but I believe downloading the trial of that redirector you will reproduce the problem first shot.