Version details: 1.5.5 under KDE
Distribution/Version: Debian unstable

I've noticed that, if I create a chart and add some titles to it, when I close 
and reopen the file all titles have disappeared. A simple test case would be: 
 
1) Open Gnumeric with a blank sheet 
2) Enter the numbers 1,2,3 in the first column 
3) Select them, and insert a new chart 
4) In the chart dialog, add a title 
5) Click finish and place the chart 
6) Save the file to test.gnumeric, close Gnumeric 
7) Open Gnumeric, open test.gnumeric. Chart title will be gone or an error 
will be in his place 
 
This happens with all titles, either global chart titles or axis titles.