bit rate conflict?

[istyle]

anyone ever experienced this problem?
becos my audiocard is gina 20bit so it causes this
i tried to improve my recording by changing bit rate in cakewalk's audio option from 16 to 20 and 24
sure this improves a lot
but big problem comes along when i have to save it as BUN
and later add more recording to it without changing the bit rate to its original ( i think this causes the prob )
so when it was saved to bun it can't be open up again,sure with cake
i tried several time to detect the problem
by recording an extra to it with 20 and 24 to find whether which one caused the conflict but couldn't get a summary of the result sometime their bun can be opened sometime they can't
can anyone figure out what's the real problem with this?
and how to getsround it
thnx in advance