The first thing I'd suggest is to vary the tx_power and 
rx_sensitivity parameters to the stir4200 kernel module.  
Considering that the devices appear to be interoperable to 
some extent, this really looks like a signal quality issue.  
Also, you can try to vary the distance between the phone and 
the dongle.  About 6 inches to a foot is ideal -- closer 
doesn't necessarily mean better signal quality.  See if 
either of these help.

After intalling the module, to try out these settings do:

    insmod stir4200 rx_sensitivity=3 tx_power=2

rx_sensitivity, the seceiver sensitivity, varies from 0-7; 0 
is most sensitive.  tx_power, the transmitter power, varies
from 0-3, 0 is highest power.

The best settings depend on which physical transceiver is on your
particular str4100-based hardware.  This is indeed why there is a
settable parameter.  Unfortunately, there is no programmatic way
to detect what transceiver is attached.  In fact, the only way
Windows gets this parameter correct is that the ".inf" in the
windows driver that was shipped with the dongle presumably had a
value correctly preset.  Alas it's not in a form that I could
translate directly for you into sensitivity/power values.