Symptoms

1. You are using Firefox 9 and above
2. Copied cells from an Excel spreadsheet, and pasted it into a Confluence 4 editor
3. Instead of being generated as a table, the cells are displayed as an image, so you can't edit the values in the table from within the Confluence editor

Cause

This is a Firefox bug, documented here: https://bugzilla.mozilla.org/show_bug.cgi?id=714115

Workaround

1. Navigate to Windows Control Panel >> Region and Language >> Additional Settings, which should bring up the Customize Format message box
2. Change the Decimal symbol from comma (,), to a period (.)
3. Save the settings, restart Windows and relaunch your FF browser and try to copy paste the table again