unlimited 'Items to display' not working properly

I have the following issue:
I am displaying a large number of items in a view
basically there is first a page with exposed filters and a table preview and then attached a feed to export the data as an xls file
initially the "items to display" on the page were set to a smaller value (i.e. 10) and the xls download to unlimited
everything was working fine, I then realized that when the number of rows as a result of the exposed filter settings reaches 7200, I get an error on the feed (file not found), the page is still displaying fine thanks to the pager
first I thought there is a size issue with the xls feed
but when setting "items to display" to 0 for the page I end up with a white screen (when the number of items due to the filter settings reaches 7200)

thus my question is there a size limit overruling the "items per page" or what could be the reason for this behavior

thanks for any help