This is getting interesting.....
I would think, with all respect for those that advised so, that Sakis3g isn't needed for meanwhile famous and random available Huawei USB modems.
If you use PCC, is your provider there actually listed? (If so other details will be there provided, i.e. APN, user/password. If not, not needed)
Does the modem shows running a konsole with command lsusb?
Does maybe your provider gave you specific details like APN and user + password? (If not listed, just in case)?
There got to be a "clue" overseen here.
Start from square (and remove Sakid3g). The non recognition of the USB modem can be caused by a non supporting kernel (which one do you use?). Or a service not running (hal daemon runs?).
Once detected, this should be a piece of cake for both PCC and UMTSmon (and even kppp although that asks for some more configuration).
If you try again, remove all existing connections to be sure you won't confuse the system (or yourself,
If UMTSmon is your choice (and your modem is detected), go to "select network operator" and "have the card decide".
Then you have to add a "profile" and make sure (under Edit) that you uncheck "replace default route".(The thing that kept me for years from being able to use UMTSmon and drove me crazy at the same time)
That should work .
Of course I see your problem "modem not detected" and it is my believe THAT (and that only) is the problem.
This might be solved in a next kernel upgrade (I guess and hope for you ....)
Sakis3g got it working for you but clearly in a buggy way so far. There got to be a better way.
Sorry more "thoughts shared" then actually help but you might have reached the same conclusion already. Your modem seems not supported by the kernel you use.