I have an iGrid with 120,000 rows and I am doing a loop for testing purposes changing each row's date.
the problem that I am having is that while this apps function is running, everything is frozen on the app for about 10 seconds
then after its fine and all rows are updated.. what can I do so that the app doesn't lock ?

As I can see from your posts on this forum, you are using WinFroms.NET and iGrid.NET. In this case, if you use the standard technique to populate the grid or change its cells (i.e. simply write your iGrid related code in form or form control events), you are doing this in the main thread of the app. The main thread is also responsible for the interface, and if it is busy while you are working with iGrid, the user cannot use other controls on the form. This is not a problem of iGrid, it's a common problem of any other visual control like ListView or DataGridView.

To solve your problem, you need to use a separate thread to work with iGrid. We have an example of this in the main iGrid demo - see the sample named 'Multithreading'. But note that writing a multi-threaded UI app is an enough complex task as it may concern all other parts of the interface.

Last but not least, in a single-threaded app you also need to wrap your code that changes a lot of cells with the BeginUpdate/EndUpdate calls. BeginUpdate temporarily disables any update of the grid on the screen, and your code performs much faster.