devc-ser8250 high baud rate hangs

Hi,

Modem connection with high baud rate (115200) hangs after dial in.
56k Baud is OK.
For an ISDN terminal adapter (64kbit data rate) I need the high baud
rate definitely.

I tried it with different parameters for devc-ser8250 - but no success
until now.

Is there a solution ?

Thanks