ITunes Disables My Internet On Vista 64-Bit

Question

I don't know if anyone has ever heard of this issue, but let me detail this as much as I can, and see if anyone knows of a work around...
So I recently set up my girlfriend's network, with her ISP's modem and a Linksys wireless router (http://www.linksysbycisco.com/US/en/products/WRT54GL). I set it up with wireless security (WPA-Personal). I connected to her wireless network with her computer, an HP laptop running Windows Vista 64-bit, my Acer Aspire One (ZG5) running Windows XP SP3, a Dell Inspiron 600m running Windows XP SP2 and my iPhone 3GS, with the 3.1.2 OS. All were able to access the internet flawlessly, with NO issues.
I then bought her a 5th Gen Nano. When I ordered it, I told her to start learning iTunes, so she downloaded it, and was looking around it. This is when the issues started...
She was still able to get online through IE, and she downloaded Windows Live Messenger. However, it would not connect for her.
She was e-mailing me later that night, and everything worked. However, the next day, she called me, informing me that the internet was now inaccessible...
I came over to check on the network, and my laptop connected to her network, but had a sketchy internet connection. Now, please don't misunderstand that, as I had a 5 bar, immensely strong and stable connection with her WiFi, as I was sitting right next to the router. When I used IE (and FireFox), I would be able to access Google about once every 5 attempts.
Her computer (the HP) could not connect at all. My iPhone seemed to be doing okay with the connection. I pinged Google and Yahoo! from the CMD Prompt, and was always given a reply each time.
I couldn't figure out what was going on, and she had been making a comment about wishing her computer was back to the way it was, so being that most Vista laptops (from what I've experienced) have recovery partitions on the HDD, I reformatted it and restored it to the "out of the box" defaults.
Everything worked good then. All devices were able to access the internet EVERY TIME attempted.
I then installed iTunes 9.0.1 again on her computer, and that's when the issues started again. Once everything was installed, it gave the network issues. I had internet issues (not CONNECTION issues with the router) with my laptop (the Acer). My iPhone was unable to access the internet from here, and I had to pop over to the 3G network.
To rule out ANY conflicting software, I pruned her computer and removed all unnecessary software that had been reinstalled through the reformat restore (trial burning software, trial ISP stuff, etc.). I could still not access the internet through any of the three devices. This time I had NO successful attempts, as I had last time.
However, here's the two things that really irritated me to no end. On her computer, Windows Update was actively downloading the updates. However, nothing else that accessed the internet was working (Live Messenger, iTunes store, IE, FireFox, etc.). And my computer wouldn't work online. Nothing...yet pinging different websites still responded...
Anyways, I uninstalled iTunes on her computer and magically the "block" on the internet was lifted. All three devices were able to access the internet with no issues at all...
When I got home later that night, I looked into the issue a little, and noticed that apparently iTunes has some specific conflictions with HP and Logitech drivers, especially when it comes to Vista, and this IS an HP computer. However, what baffles me is that iTunes being installed on JUST HER COMPUTER seemed to put a block on the internet from the wireless router...I would've thought if there were an issue, it would've just blocked her computer from the internet, not mine and my iPhone...*it was as if iTunes on her computer cut the connection from her modem to her wireless router*...
What gets me even more is that I have iTunes 9.0.18 on MY laptop, and it caused NO conflictions with her network...I'm baffled...this is just goofy for me to have to find an alternative to iTunes JUST FOR HER COMPUTER, otherwise it pretty much takes down her internet connection, YET NOT HER NETWORK!!! And what gets me even more is that Windows Update WAS STILL DOWNLOADING UPDATES!!!
I checked her WiFi router settings when I re-set it up, and all restrictions were off, and any permissions that would cause a block in the network by unknown stuff were off...I just don't get it...anyone have any insight on this?
If you have any questions for me, to get more detail to help me rule out this issue, just ask. I'd REALLY like to reinstall iTunes on her computer, instead of another program. I've actually downloaded the older versions of iTunes (as in my research, I read that anything after 7.7.1 apparently causes issues with Vista running HPs, due to some driver or file incompatibility...). Hoping that 7.7.1, 8.0, 8.2.1 or 9.0 (not 9.0.1) can resolve this, so at least she can still use iTunes...
*HELP!!! Please!!!*

Answer 1

It is not just the HP. I have 3 HP computes and 2 Dell computers. 2 of the HP and 1 Dell suffer the iTunes internet block. Took me a while to figure it out also. But, the one thing that is different on the Dell, is that I can leave iTunes installed and not open it and everything works. As soon as I open it, internet access goes down. BUT secure sites (https:) works fine.