It's very common for the major airlines to change their schedules around. This was true even before the economy tanked and 9/11. It is unrealistic to expect that all of your arrangements will stay the same if you book far in advance. This is one of the "risks" we accept when we book in advance on the major airlines.
I learned early on that I should periodically check my reservations so that I could find out about any changes more quickly. If the changes don't work for your plans, the earlier you call to adjust, the more options you have.
For example, I once booked non-stop flights on NWA (MSP-MCO) about 9 months in advance via the NWA website. NWA changed the schedules and reassigned my party to flights that connected in Memphis. Since I value non-stop flights, I called to see what could be done. The agent explained that their computer was programmed to reassign people so that they left as close to the original departure time as possible. (Makes sense, I guess, but I don't know if all the airlines use that criteria for reassingment). Anyway, there was not a problem moving us back to non-stop flights at a different time. (Prior to the call, I looked up the options and knew what I wanted). We did not pay either a change fee or additional $$ for the airfare itself. Have done this many times and the key is to find out about the change as soon as possible, know youur remaining options and call right away. Sometimes your best option might be a refund so that you can rebook on another carrier.
That same incident is also when I found out if you do not purchase all of your parties tickets at the same time, the airline considers them separate reservations. Also, if some are FF reservations and some are not, they are also separate reservations. With separate reservations, the airline has no way to know that you are traveling together when changes must be made due to their schedule changes. If changes are made, you may or may not end up on the same flight and you may or may not end up sitting together (most likely not for the latter).
My point is that one should expect changes, even multiple changes, when booking in advance. That is especially true given the current conditions. Check frequently and call as soon as you notice the change (if you don't like it). Polite requests to be moved to something more workable have always worked for me. If you call at the last minute or don't know about the change until close to your departure date, your options will be limited. The airlines do not usually notify passengers about schedule changes until a week or two before departure (probably because of the possibility of more changes). That is usually too late to do very much. The airline cannot move you to a flight that doesn't have seats left.
HTH.
We had booked our flights 10 months in advance. 
