Triggered the beach ball but can't figure out why

Question

For most of what I do 10.0.3 works reasonably well. From what I've learned here I know to use Event Manager X and Preference Manager. I only open the event(s) and project I need and have generally managed to avoid hanging the system. I've found title rendering brings FCPX to its knees so I only do titles when I've got lots of time.
Yesterday I was working on a relatively short project. It's about 6 minutes long, has very few titles and only 3 or 4 cross dissolves. I was fine tuning a number of edit points to match the beat of the soundtrack. This involved adding markers and then moving the edit point as appropriate. For the first 50 or so edits this worked easily and quickly. There was no background rendering or anything else I could see interfereing with the activity. Then suddenly on one edit the beachball showed up and FCPX wouldn't respond. After ~15 minutes the beachball was still spinning and FCPX was still locked up. Did a force quit, restarted and went back to assess the damage. All my changes were ok except for the one that hung the program. Redid it and all was fine.
So my question is can anyone speculate what triggered this? If I'm doing something that causes this I want to understand so I can work around it or aviod it next time. Work arounds to evade bugs seem to be part of using FCPX at this stage.
Macbook Pro (2011) OSX 10.7.3, 2.4 GHz, i7, 8Gb RAM, FCPX 10.0.3
Thanks,
Ed

Answer 1

while C1%found loopData can not be found before fetch.
set serveroutput on
declare
d2 dept%rowtype;
cursor c1 is select * from dept;
begin
open c1;
loop
fetch c1 into d2;
exit when C1%notfound;
dbms_output.put_line(d2.deptno||d2.dname);
end loop;
close c1;
end;