Menno, the VPC god of Dynamics CRM land has created the very nice Aug 07 VPC of CRM 3. Sadly, a common error in it has to do with some new blocking of hacker attacks. It results in an error, that after a while of running it, you get a login-prompt and CRM stops working. The temporary solution is to restart IE.
Menno has written some about this on his blog, please read it. http://blogs.msdn.com/mscrmfreak/archive/2007/11/02/august-2007-vpc-fix.aspx
I personally liked "Method 1" described in the references KB-article. The details are described bellow. I have tested it for 5 minutes and it seems to be working. Here is a copy of the text:
Method 1: Disable the loopback check
Follow these steps:
Click Start, click Run, type regedit, and then click OK.
In Registry Editor, locate and then click the following registry key:
Right-click Lsa, point to New, and then click DWORD Value.
Type DisableLoopbackCheck, and then press ENTER.
Right-click DisableLoopbackCheck, and then click Modify.
In the Value data box, type 1, and then click OK.
Quit Registry Editor, and then restart your computer.
Microsoft Dynamics CRM Consultant