To resolve this issue, delete all of the files in the Temporary Internet Files folder.

To do this, follow these steps: Start Windows Explorer. Browse to C:\Document and Settings\User Name\Local Settings\Temporary Internet Files. On the Edit menu, click Select All, and then press DELETE. When the confirmation message appears, click Yes. Close Windows Explorer.

View Source Not Working in Internet Explorer
http://www.winguides.com/registry/display.php/1246/

Source Code Is Not Displayed When You Click Source on the View Menu in Internet Explorer http://support.microsoft.com/default.aspx?scid=kb;EN-US;Q306907