having same problem in newly installed FC2, but mysteriously after about 10th boot for no apparent reason, I was able to make the device active and get online. Up until then kept getting (error6 or 8). The modem still does not show up in the hdwr browser. Also kudzu "found" the modem during about the 20th bootup, but the modem still does not show in hdwr browser or in /dev/.
Also this modem connects with confirmation in Kppp, but neither browser can make connection, even tho both browsers CAN connect in the internet conf wizard.
I had no problems with DSL(LAN), external serial modem, or internal PCI modem and Kppp in Mandrake 10.0 (on same PC/modem)..........go figure.