Reporting Services Online Sort and Paging Service with ReportViewer

I'm having a strange issue with interactive sorting and paging in ReportViewer that I can't figure out. I am using a local report definition and a ReportViewer control in an aspx page. I have AsynchRendering set to true. Everything seems to work fine except for this problem. Below are the steps to reproduce the problem:

(page 1 before all sorts)
COL1 | COL2
  a 1
  c 3
  b 2

1) While on page 1, sort ascending by COL1 - sorting is correct

(page 1)
COL1 | COL2
  a 1
  b 2
  c 3

2) Go to page 2 - sorting is correct

(page 2)
COL1 | COL2
  d 4
  e 5
  f 6

3) Sorting in descending order in column X (after that automatically returns to page 1) - sorting is correct

(page 1)
COL1 | COL2
  z 26
  y 25
  w 24

4) Go to page 2 again - sorting is wrong; the data is still sorted in ascending order, as if not sorting on page 2 on page 2

(page 2)
COL1 | COL2
  d 4
  e 5
  f 6

Other strange things:

• If I go to any page other than page 2 from page 1 the sort order is correct, and if I go to page 2 from any page other than page 1 the sort order is correct.
• If I set AsyncRendering to false I don't have this problem at all. I need AsyncRendering to be true.
• This issue only occurs in IE6 and IE7. I don't meet in Firefox or Chrome.
• Here's the weirdest = this problem only occurs after I deploy to the web server. If I run it from the Visual Studio 2008 development server on my computer, everything works fine without exception.

This is a problem because the corp I work in mostly only uses IE6 / IE7, this sorting feature is a must, and the page is too slow if I don't use AsyncRendering.

Any help with this would be much appreciated.

(comments from the answer I made before I had enough reputation to be able to comment): There is something else I noticed about what is going on with this. using fiddler I was looking at each click-by-click HTTP request / responses and navigation and I noticed that there is no HTTP GET request when navigating from page 1 to page 2. all other navigation clicks and click sorting make a GET request and then the html is updated with the appropriate response. if there is no GET request when navigating from page 1 to 2 after another sort has occurred, the page will not be refreshed to the current sort order. this looks like a ReportViewer AJAX error to me ...