Error loading in Custom UI XML when starting outlook

Hello,
I get the following error message every time I start OUTLOOK or open an email message. The error says “Error Loading in Custom UI XML”. I have tried to install the program again but the error exists. Provide resolution to fix this error. Thanks in advance.

Error Loading in Custom UI XML:
Line: 1
Column: 79
Error code 0x80004005
Unknown Namespace: http://schemas.microsoft.com/office/2007/10/customui
Element: Custom UI
