1. Create a new Writer Document.
2. Change the current font size to 14 and write "Aaa Bbb Ccc", then Enter.
3. Double-click on "Bbb", change its font size to 18.
4. Place the cursor at the beginning of document, before "Aaa".
[ I'll shortly attach a file with steps 1-4 already done ]
5. Edit - Find & Replace - enable "More Options".
6. Click in the "Search for" field, leave it empty, Format - Font - Size - 14. 
7. Click in the "Replace" field, leave it empty, Format - Font - Size - 24. 
8. Click the "Replace All" button.

Expected: text having size 14 is changed to size 24.

Actual result: OOo freezes. It actually asks whether to disable the Undo
function or not, answering No leads to the message "Replaced 60.000 times" while
answering Yes causes a freeze, with OOo entering a seemingly infinite loop.

[Found during Italian QA tests; the simplified example is due to Renzo Bianchi]