Hello, I am posting here hoping somebody may recognise this problem. I've suddenly started experiencing a frustrating random problem with Excel 2010, which I run in Windows 10 under Parallels Version 12.1.3 (41532) on an iMac. Whenever I need to delete columns or delete rows from an Excel spreadsheet, at some unpredictable point part way through the process Excel crashes every time. After rebooting, the error message always says: "One or more invalid conditional formats were removed from the workbook". In the original file that failed, I've gone right through and thinned out and simplified all of the conditional formatting, but to no avail. I have also spent hours trying to isolate when the problem started occurring, but it is not just on files I have edited recently or after any known event, and can happen on any old file I try. I tried doing a System Restore only to find that it had been turned off so that was useless. I did run a repair of Office 2010 but nothing improved. I have tried running Excel in Safe Mode but the problem still occurs. This has cost a lot of lost time and unreliability with my work and I am no closer to a solution. The only thing I did notice is that there seems to have been a major update of Office 2010 and Windows in the last day or two. Has anyone any advice on how I can fix this please? Thankyou for your assistance.