I love using Mobile Shell 3.5.3, and I love using Windows Mobile 6.5.3, but the facebook and twitter widgets would not connect for me. I kept getting the error cannot connect. It was driving me nuts and forcing me to switch to a regular 6.5 rom. I figured out that 28002 was the last 6.5.3 build that these widgets worked on, so I pulled some packages out and added them to the new builds and viola! it worked. I've narrowed it down to the webview.dll file. This works fine for me when I cook it in, and I've tested the cab a few times. The widgets can connect now, and Internet Explorer doesn't seem to be affected. I don't use it all that often so I can't really say for sure if it makes a huge difference.
The cab is hard-coded to go to the windows directory and cannot be uninstalled. So this is kind of a one-time deal.
This is only a test and will need some feedback from others before we can call this one a sure thing.
BACKUP YOUR PHONE BEFORE YOU TRY!
I AM NOT RESPONSIBLE FOR WHAT THIS MAY DO TO YOUR PHONE!
USE AT YOUR OWN RISK!