C# .Net 1.1, page keep on loading/hang after gone through all the function

 i have a C# .Net 1.1 page, where it will do the following :
 - query DB
 - write the data in .csv
 - zip the .csv
 - Response.Redirect the URL link for the .zip
The data size is very much depends on the date range that being choose. if short date range, means the data size is smaller and process time is faster, then everything is fine.
but if long date range, the above action takes about 8 minute to complete, then IE will show page keep loading until the session is timeout. i put a logfile and find that the code is actually already finish running, but then the page is keep on loading, or hanging there.
any idea  what cause this? and any solution of this?
thanks in advance for your help.
...