Hi,
1. Let's say I upload an Excel document: somefile.xls
2. I update this file with a plain text file: otherfile.txt
3. The contents are overwritten but the title is still somefile.xls
4. Inline editing isn't possible although this is just a plain text file
4. I update this file again but with a picture this time: somepicture.jpg
5. The contents are overwritten but the file is useless because Alfresco still thinks this is an Excel file
Maybe some MIME type testing before updating wouldn't hurt? Don't know what direction would be best here, maybe the update of an Excel file with a plain text file is still acceptable but the JPEG certainly isn't, isn't it?