Here's my experience with the 4.0 upgrade on Verizon Wireless with the 7750.

1.) followed the instructions here...
2.) enjoyed new 4.0 operating system
3.) noticed I could no longer send e-mail from my BB.
4.) called Verizon Wireless and complained.
5.) was instructed to wipe my device with the failed password 10x
6.) said, "$hit" what do I do about this 507 error?
6a.) was told to return the device to a Verizon Wireless store.
6b.) continued to read the forums for a solution to the error.
7.) downloaded the 3.6 desktop manager
8.) downloaded the 3.7 operating system
9.) reinstalled the desktop manager and operating system
10.) started once again using the 3.7 operating system...


So basically, the 4.0 install worked... obviously though I didn't have an experience with the web browser because it's not supported... I however did not expect to have the problem sending e-mail... So if you're experiencing problems sending e-mail on your VZW 7750 after upgrading to the 4.0 OS... either please suggest to me how I can still send e-mail after the upgrade... or follow along with these instructions so you can restore your BB to the factory original state and again have full functionality.