Problem with Gnome 2.2 and USB modem driver

[Guillaume <Maximilian87 wanadoo fr>]

Hi,

I recently upgraded from Gnome 1.4 to 2.2 on Debian3.0 (kernel 2.4.1) 
and I experienced some really weird problems :
when I try to connect to the net with my dsl USB modem, all open 
nautilus windows freeze, as well as the desktop. I can't click on the 
desktop's icons any more, and nautilus can't be launched either. What's 
funnier is that when I move a window over an icon on the desktop, it 
sort of rubs it out. Plus, Gnome's "Log Out" button becomes ineffective.
 However, the top and bottom panels still work perfectly well and any 
application (apart from Nautilus filemanager) can be launched from them.
I must add that this problem occurs equally when I'm logged as root and 
as normal user, and only when I try to connect to the Internet (in 
normal time, things work perfectly well).

I use the following sequence of commands (as root)
to connect to the net :

mount -t usbdevfs none /proc/bus/usb
modprobe n_hdlc
modem_run -f /etc/ppp/peers/mgmt.o -m
pppd call adsl ---> at that point, nautilus starts bugging


and here's the contents of the "adsl" file

debug
kdebug 1
noipdefault
defaultroute
pty "/usr/local/sbin/pppoa3 -m 1 -c -vpi 8 -vci 35"
sync
user "<my_user_internet_login>"
noauth
noaccomp
nopcomp
noccp
novj
holdoff 4
persist
maxfail 25
usepeerdns

Any solution/suggestion is welcome, since this little bug is really 
getting annoying :(

Thanks in advance.