When you open the invitation to make a change for only a specific date, make sure you open it only for that date and not for all dates. When you double-click on the meeting request, it will give you the option to open just that occurrence or the series. Make sure you select just that occurrence. It will send the updated information to all attendees but it will only be for the date you changed, not for all dates.

I have had the same problem and I have done what has been suggested above and still Outlook fail to send the correct date, time, or comment within the meeting invite. I have had IT to look at it in order to find out what was going on and to no avail any thing was resolved. I have other admins within my organization to have the same problem. I was so frustrated last year because Outlook made me look as if I didn't know how to send out an update recurring meeting that this year I had to make changes to how I would send out my meeting updates. Because my boss has two standing recurring meetings weekly it was very difficult in updating the recurring invites. I believe there's a glitch within Outlook especially if you are working out of a PST folder. IT creates a PST folder when you have reached the capacity of memory in Outlook and you need to keep all the folders you have created (which I had over 20 folders) to dump emails into them in Outlook but you can't send or received emails. This is when a PST folder is created and you can continue to send and receive emails plus create additional folders also you will still have access to your original emails and folders that you can continue to dump emails you want to hold onto until a certain date. I noticed this was when I began to have problems with Outlook in sending recurring emails. I don’t know if the original Poster with this problem working out of a PST folder, but this was when me and the other admins began having our problems.

I suggest that you try Meetingwizard.com.
It is easy to use and it's FREE!