https://community.graphisoft.com/t5/Installation-update/Can-t-quot-re-open-quot-a-AC10-file-in-AC9/m-p/77619#M9269 You can also try saving it back to AC9.0 format under "Save As" and selecting the AC9.0 format option. Tue, 19 Jun 2007 23:33:42 GMT Richard Morrison 2007-06-19T23:33:42Z https://community.graphisoft.com/t5/Installation-update/Can-t-quot-re-open-quot-a-AC10-file-in-AC9/m-p/77617#M9267 <DIV class="actalk-migrated-content">I accidentally opened a AC9 file in AC10 and then saved. When I try to re-open in in AC9 it gives me the attached error.<BR /><BR />What can I do?</DIV><BR /><IMG src="http://community.graphisoft.com/t5/image/serverpage/image-id/70857i6FC28C2284F39CEC/image-size/large?v=v2&amp;px=999" border="0" alt="Picture 1.jpg" title="Picture 1.jpg" /> Tue, 09 Jul 2024 06:32:18 GMT https://community.graphisoft.com/t5/Installation-update/Can-t-quot-re-open-quot-a-AC10-file-in-AC9/m-p/77617#M9267 Anonymous 2024-07-09T06:32:18Z https://community.graphisoft.com/t5/Installation-update/Can-t-quot-re-open-quot-a-AC10-file-in-AC9/m-p/77618#M9268 Do you see an .LCK file in the file directory? If so delete it and re-attempt. Tue, 19 Jun 2007 23:13:10 GMT https://community.graphisoft.com/t5/Installation-update/Can-t-quot-re-open-quot-a-AC10-file-in-AC9/m-p/77618#M9268 Aaron Bourgoin 2007-06-19T23:13:10Z https://community.graphisoft.com/t5/Installation-update/Can-t-quot-re-open-quot-a-AC10-file-in-AC9/m-p/77619#M9269 You can also try saving it back to AC9.0 format under "Save As" and selecting the AC9.0 format option. Tue, 19 Jun 2007 23:33:42 GMT https://community.graphisoft.com/t5/Installation-update/Can-t-quot-re-open-quot-a-AC10-file-in-AC9/m-p/77619#M9269 Richard Morrison 2007-06-19T23:33:42Z