I have developed an ASP.Net application which users use to enter their time sheets. The application is using an UltraWebGrid to display the days as columns and the entries as rows. Whenever the user enters values to the cells, signifying the hours spent for a particular project on a particular day, I have a JavaScript function which updates the column totals for the day. When the user focuses another row, the row total is also updated.

A strange behavior is exhibited when the number of rows of the grid exceeds 50 or so rows: when a new row is added to the grid, after the user populates the first cell, it takes up to 40 seconds for the total of the column to be updated, during which time the browser is waiting for the operation to finish. After control is returned to the browser, populating subsequent cells in the same row update the totals instantaneously. When a new row is added, the same behavior is exhibited.

Could someone please point me to where I should start troubleshooting this issue? Is this browser related (we are using IE 8), or should I look into the JavaScript code?