FIX
In CrossOver:
1. Choose "Programs" menu
2. Choose "Run Command..." item
3. Use bottle containing Xara 7
4. Browse to "~/Library/Application Support/CrossOver/Bottles/Xara Designer Pro 7/drive_c/Program Files/Xara/Xara_Designer_Pro_7/XaraDLLs/WebFileUpdater.dll"
5. Choose open on "WebFileUpdater.dll"
(path may appear differently to above)
6. Add regsvr32 before file path as follows:
Posted:
regsvr32 "~/Library/Application Support/CrossOver/Bottles/Xara Designer Pro 7/drive_c/Program Files/Xara/Xara_Designer_Pro_7/XaraDLLs/WebFileUpdater.dll"
7. Click run.
The WebFileUpdater.dll is now registered, and the error will no longer appear.