Hi Terry!
Couple rapid fire things that first come to mind to check try for ya. make sure you save your drawing and maybe make an extra backup copy of it while testing the things below.
- Locked Layer?
- Layer Search off?
- Close and re-open the drawing
- Restart Datacad
- restart windows
- Maybe try running a Repair on the file?
- Try purging unused symbols via the symbol browser's options button
- Could the path to the symbol's location on the hard drive be really long like over 260 characters?
- Could the symbol have a special character in the file name or path, Examples: !@#$%^&*()
- if it's just one symbol having the issue, can you insert it or copy/paste it to a new drawing and see if it will explode there? If you can, try deleting all instances of the bad symbol in the drawing, do a symbol purge, save and close the drawing and re-open the drawing and try going from there.
Let us know how it goes for you or if you need more help!