Palm m515 serial communication problem

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I have a PIC microcontroller based application, which uses a serial terminal
for setup. On a M515 the communication does not work, using the "Online"
serial terminal  SW the Palm read the PIC ok, but sending data the other way
is extremely erratic. Serial communication with other similar applications
works ok, so it seems to be related with my project. Such communication
works ok with III and V series Palms, and also on T3 once the serialfix is
instelled. One curious thing with 515 is that if I put on "local echo" (the
PIC echoes the communication, so normally LE should be off), I see that the
Palm does not send all characters typed in, but only every now and then
sends a big burst of stuff (multiple repeats), which is then mis-interpreted
by the PIC. On working units every single character is sent (or at least
echoed) right away.

So what gives? Any suggestions what to do? Could it be related to
handshaking or flow control? But then, "online" does not give any options to
change those (on OS3.x there is an option to select the handshake
procedure, but not on OS4)...



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