With IE 7 there is a security feature that can prevent CRM from auto logon. Here is how to correct it:
1. Click Start, click Run, type regedit in the Open box, and then click OK.
2. Locate and then click the following registry subkey: HKEY_LOCAL_MACHINE\Software\Microsoft\Internet Explorer\Main\FeatureControl\FEATURE_SUBDOWNLOAD_LOCKDOWN
3. Right-click Outlook.exe, and then click Modify.
4. In the Value data box, type 0, and then click OK.
Pasted from <http://blog.customereffective.com/blog/2008/02/crm-users-recei.html>