Thanks for the sample. It really shows the issue. About Safari please keep in mind that the gird does not support  it.  Please refer here supported environments : http://es.infragistics.com/support/supported-environments.aspx#SupportedEnvironments

Please can you create a support ticket  and please refer this forum about the scrolling issue.

Thanks you!

I did try using width="100%" - this seems to be a valid work around.

However in safari, it give an infinitely expanding width horizontal scroll bar

But using a specified width in IE, it keeps expanding horizontally.

OK.  Finally could recreate.

I have created a sample

http://63.170.253.111/default.aspx (default2.aspx has what it looks like in our app)

group by "student"

expand any row

If you are running IE < 8 or running in IE8 (in compatibility mode) your browser will hang

However

If you are running IE8 NOT IN COMPATIBILITY MODE, the grid will keep expanding horizontally - watch the scroll bar.

FireFox 3.6 seems OK, FireFox 3.57 seems OK

I used the grid as added from the toolbox - no edits to any properties EXCEPT removing height and width declaration.