If you save a document this sets time zero for undo. So if you accidently open the wrong thing edit it and save it then you're screwed.
NOT reproducible with "LibreOffice 3.5.5.3. German UI/Locale [Build-ID: 7122e39-92ed229-498d286-15e43b4-d70da21] on German WIN7 Home Premium (64bit) Problem has not been confirmed @ffs: Thank you for your report – unfortunately important information is missing. May be hints on <http://wiki.documentfoundation.org/BugReport> will help you to find out what information will be useful to reproduce your problem? If you believe that that is really sophisticated please as for Help on a user mailing list Please: - Write a meaningful Summary describing exactly what the problem is - Attach a sample document (not only screenshot) or refer to an existing sample document in an other Bug with a link; to attach a file to this bug report, just click on "Add an attachment" right on this page. - Attach screenshots with comments if you believe that that might explain the problem better than a text comment. Best way is to insert your screenshots into a DRAW document and to add comments that explain what you want to show - Contribute a document related step by step instruction containing every key press and every mouse click how to reproduce your problem (similar to example in Bug 43431) – if possible contribute an instruction how to create a sample document from the scratch - add information -- what EXACTLY is unexpected: There is nothing like "time zero", but an undo stack -- and WHY do you believe it's unexpected (cite Help or Documentation!) -- concerning your OS (Version, Distribution, Language) -- concerning your LibO localization (UI language, Locale setting) –- Libo settings that might be related to your problems (video hardware acceleration ...) -- how you launch LibO and how you opened the sample document -- everything else crossing your mind after you read linked texts
Closing Bug due to reporter's inactivity as INVALID due to lacking information. @reporter: Please feel free to reopen this bug if you find out that the problem still exists with the current stable LibreOffice version and if you can contribute requested additional information due to <http://wiki.documentfoundation.org/BugReport> (especially BugReport Details)!