Version:           4.3.3 (using KDE 4.3.3)
Compiler:          gcc version 4.3.4 (Gentoo 4.3.4 p1.0, pie-10.1.5) 
OS:                Linux
Installed from:    Gentoo Packages

steps to reproduce:

rm std.ics (clean start)
start korganizer
create a new event without associated time for a day in the future
set the recurrence to 'daily', ends on a date 2 or 3 days later
'ok' out of dialogs, exit korganizer : (1) below
restart korganizer
-> event looks correct
open 1st day of event, recurrence now ends 1 day sooner (bug)
click 'ok' -> std.ics gets updated, last day of event disappears in calendar
exit korganizer : (2) below
- continue process, can get end of recurrence to before start

the rrule in the std.ics entry is changing:
(1)
RRULE:FREQ=DAILY;UNTIL=20100122
DTSTART;VALUE=DATE:20100120
DTEND;VALUE=DATE:20100121

(2)
RRULE:FREQ=DAILY;UNTIL=20100121
DTSTART;VALUE=DATE:20100120
DTEND;VALUE=DATE:20100121

a less-bad variation occurs if the event has a time associated: on re-opening korganizer, the start and end of the event are shifted 1 day earlier.  opening the event shows the correct dates and recurrence, clicking 'ok' resets the calendar display correctly.  the std.ics file does not appear to be changed.

korganizer time zone is  TZID:Africa/Lagos, system settings Date & Time is Africa/Lagos (WAT), however 'Country/Region & Language' is set to United Kingdom (if that matters here).