Error messages when logging into WP

Hi Everyone-
I’ve been plagued by error messages like the one below when I log into my WP control panel:

Fatal error: Call to undefined function get_taxonomies_for_attachments() in D:\INETPUB\VHOSTS\thedenverliquorbarn.com\httpdocs\wp-admin\menu.php on line 67

The hosting company was little to no help (I’m never using Whois again!), at first telling me to verify permissions (which I did, no help), and then just telling me to do a manual update. I’m reluctant to mess with the manual update, since I don’t see how it will fix these ongoing permissions errors. Can anyone point me in the right direction to get this fixed? I currently can’t access any of the back end of the site, I just get a page with this error message.

Thanks in advance for any help!