resetting the layout and clearing the cache should correct those sorts of errors, sounds like the configuration folder has gone corrupted.
rename the
C:\Users\Levin\AppData\Roaming\Adobe\DreamweaverCS5\en_US\Configuration\
folder that a contains the cache file.
after renaming the configuration folder, start dreamweaver to recreate it. and close DW.
then open the extension manager, in the extension manager remove all extensions, then reinstall them.