Can I ask. How long did you wait. Some users have reported a long time for open/save dialogs. (up to 45 seconds I think)
The only thing I can think of at present. Is to try deleting the file history.
With TurboCad NOT open. on Windows 10. Go to C:\Users\Your Username\AppData\Roaming\IMSIDesign\TurboCAD 2018\Professional x64\Data\History (or whatever hard drive if not drive c:\). if you have file extensions showing, rename History.txt, to History.old. If file extensions are not showing, either turn them on, or copy/paste the history somewhere else, before deleting the history file. TC will recreate a blank history when next opened.
Start up TC and see what happens. If it made no difference then, go back and delete the newly created history, and rename the .old, back to .txt, (or after deleting the new one, copy/paste the old one back in).
If the above did not work, you could try deleting the 'built-in' folder, similar address to above, but in the profile folder instead of history folder. but this will delete some customisation as it creates a new one and resets TC back to default. You can copy/paste the built-in folder somewhere else, so you can replace the new one, if deleting it didn't resolve the problem.