Outlook opens only in safe mode.(2003 Outlook) and outlook 2007)
1. Reset the Outlook toolbar template. With Outlook close, do a search for and rename outcmd.dat file. Do the same for frmcache.dat and outlprnt files. Restart Outlook.
Outcmd.dat is located in C:\Documents and Settings\
For vista the path is C:\
2. If no joy, register two important Outlook files. Go to Start > Run and type regsvr32 OLE32.DLLDo the same for INETCOMM.DLL
(C:\Documents and Settings\
3. If no joy, an addin could be interfering. Disable Outlook Addins. Do a search for and rename extend.dat file.
4. Check if an external program running in the background is interfering with Outlook. Check Firewall, antivirus, antispyware, antispam, and all Norton programs. Disable these programs one at a time.
5. If no joy, create a new Outlook profile.http://www.outlook-tips.net/howto/profile.htmhttp://support.microsoft.com/kb/829918
Also try this one
1 If no joy, an addin could be corrupt. Disable Outlook Addins. Go to Tools > Trust Center > Add-Ins disable the addins.
2 . Repair Outlook. On the Help menu, click Office Diagnostics.
3. If no joy, reinstall Outlook. Go to Add/Remove Programs and highlight Microsoft Office. Click on Install/Uninstall. A menu will pop allowing you to choose repair or reinstall.