I have a grid without paging and scrolling enabled since we want to list all entries together. It has a GridClientSelectColumn column and only 2 data columns. Usually the data is 100 rows or less, but In certain cases, it can be 1000 or more. In those cases, if I scroll down to the bottom, the first item I select take 2-3 seconds to occur and then throws this error message...
"Stop running this script? A script on this page is causing Internet Explorer to run slowly. If it continues to run, your computer might become unresponsive."
The prompt has a Yes/No option to click. We obviously don't want this. For what it's worth, when the script error pops up, the row is selected, so it appears the script was waiting for the selection to take place before throwing the error. But again, it's only on the first selection; after that, further row selection is instant.
Don't know if this helps, but if I remove the GridClientSelectColumn column, the error still occurs about half of the time, but not every time.