What WoW client are you using – Retail, Classic Era, Wrath Classic.
Have you disabled all addons except DugiGuides?
Can you please try running the Dugi Installer from here and then click Settings, click Repair, click Okay three times. Finally click Okay then click Reinstall button.
Please post back with the answers and result.
If the issue stops after disabling all addons except dugiguides then it would be interference from another addon. The ‘error’ you provided is called a taint and world of warcraft blames random addons, though it does disclose that DugiGuideViewerZ is the ‘culprit’ but it would actually be another addon / macro / script that is the real cause. That’s why we ask to disable all addons except dugiguides.