Created attachment 28214 [details] Minimal test file I have a spreadsheet that opens in Excel fine. If I open it in POI and save it again, the resulting file causes the error "Protected View - Office has detected a problem with this file..." when opened in Excel 2010. It works in POI 3.8 BETA 4 but not in BETA 5. I have bisected SVN and I think r1187640 "rewrite VariantSupport to use TypedPropertyValue at max without breaking compatibility" is the revision when it started doing this. Attached is a minimal test file that exhibits the problem.
We know about this regression and working on the fix. See Bug 52385 and Bug 52337. I linked this bug report to Bugs 52385 and 52337, they all will be resolved in one go. Yegor
Should be fixed in r1244388 Regards, Yegor