Alright, I'll take a stab at this..
First off, download this program:
It is a diagnostic utility for your specific GPS unit.
2nd, if it were my money, (and it was about 3 months ago) I would have (and did) buy a BU-353, since you paid more than I did for the receiver, and i feel that having the SirfIII (I believe that's what it's called) is much better than having ANYTHING Sony made. (let the bashing begin!!) Also, their support sucks, as I am finding out right now..
Ha ha.. Anyways, we're beyond that point, so no point in shooting a dead dog..
So, what I would do, is this: Reinstall you iGuidance program. I am using iGuidance #3 and have had NO problems locking onto a signal. They say that you should let your GPS receiver sit for 15 minutes while it trys to figure out where the hell you are on this planet. But.. I've gotten a steady signal after 45 seconds or so (maybe I'm just lucky...)
Anyways, I would start with this:
1. Sit there for 15 minutes, see if it connects steadily.
2. If that doesn't work, check your port settings to confirm that you're not having an IRQ or port conflict.
3. Switch ports to confirm that it's not something to do with your port that you're using (pick 10-12 for your port, as it'll be very unlikely that another piece of hardware will use those)
4. Reinstall iGuidance (if you didn't purchase it, now is a good time since #4 came out)
5. Buy a new GPS receiver - something not Sony based
I hope maybe I helped a bit with this???