tracert timeouts on USB modem

[fusgerm]

I am using a USB modem in 32-bit Win7. It works fine for browsing etc, ping, nslookup. But tracert reports a timeout for everything but the final hop. It makes no difference if I turn off Windows Firewall.

If I put the modem in a router connected to the PC, then tracert from the PC works fine.

Also, if the modem is plugged into an XP PC then tracert works fine from that PC.

How can I get tracert to work properly on Win7 USB?

 

[fusgerm]

I have run a packet-logger to analyze traffic on the USB modem. It shows that tracert is sending out ICMP type-8 records, and that the remote hosts are correctly responding (within the timeout) with ICMP type-11 records, but tracert is reporting on only the final type-0 record received.

I have also checked the content of the type-11 records, and it is consistent with the type-8 record sent out. Indeed, the Win7 tracert has fixed some endian-bugs evident in the XP tracert.

The program "ftrace" shows the same behaviour.

I have tried disabling all firewalls, anti-virus software, running as Admin, and opening up User Access Controls.

Any suggestions?