Here's a very interesting knowledge base article about Outlook 2007 that may answer a few problems?
- Does the computer meet the system requirements for the 2007 Office suite that you are using?
- Are you running the latest version of Outlook 2007?
- Do you have a large .pst file or a large .ost file?
- Are you running a computer that has a Solid State Drive (SSD)?
- Do you have many items in a single folder?
- Do you have any nonessential add-ins or out-of-date add-ins that are installed in Outlook?
- Did you install any gadgets that integrate with Outlook?
- Is Outlook integration with Communicator enabled?
- Is antivirus software running?
- Did you install Windows Desktop Search on a Windows XP-based computer or install Outlook on a Windows Vista-based computer?
- Did the .pst file or the .ost file shut down incorrectly?
- Do you use a rule that moves items out of the default store?
- Are you connected to a POP3 server?
- Are you synchronizing many RSS feeds?
Source : support.microsoft.com/kb/940226/en-us
