The problems that you're running into are on USR's side. Luckily, they've
already been fixed in firmware updates for USRs (both V.34 and X2 models).
The exceptions are the WinModems (they still have the "pausing" problem as
USR calls it) and because there's no firmware update for the Sportster
modems with voice, they still have the problem.
For USRs that have not yet had their firmware updated, you can add the
following to the init string to fix any USR problems (except for
s32=34 Disable X2 if the modem can't even connect to the Max.
s15=128 s27=64 Disable V.42 error control (temp fix for "pausing").
For info on all of this, see:
USR firmware updates (V.34 and X2):
Also, what OS are you using in your Maxes? Our Maxes are using 5.0Ap36 and
are using Rockwell firmware version 1.140N.