Neither of the above solutions worked for me. Crash report crashreport.libreoffice.org/stats/crash_details/ebe7256a-bdc9-4277-bf8f-8c0652e8965a
Worse it even left a small window for Document recovery which was totally unresponsive and required Win Task Manager to close it! It appears that something has happened which has made LO unusable on this i5 desktop machine!. I am using Win 10 Ver 1909 Build 18363.9 I have removed LO 7.0.0.3 reinstalled the earlier 6.4 and even 6.2 which I know worked fine, but they both now crash when trying to save or save as a document. This also applies to to Calc spreadsheets. Strangely LO 7.0 works fine on my AMD laptop with Win 10 ver 2004 . A bug report Bug 136556 has been submitted via Bugzilla.
As I suspected the problem lay with one of the Win 10 updates and although Chkdsk C: could find no errors The System File Checker Utility (SFC) found errors as did the DISM Scan (Deployment Image Servicing and Management) which could not be repaired.