Internet tethering driver issue iPhone

I have an issue that I initially thought arose from the upgrade to IOS 4 on my Iphone, but now I am not so sure.
The issue is that if I connect My iphone via USB, or bluetooth, and then uncleanly disconnect it I begin to have issues with thethering until I restart my MAC. In short, when I next tether the device, Internet tehering comes on the iphone screen, and then a few seconds later disappears, and a few seconds later, comes back and so on. If I attempt to use the Internet at this time I do see intermittent Internet also so the Indicator on my Iphone seems to be accurate.
I first observed this after my IOS 4 update, but the problem seems to occur on my MAC (ie, I dont have to reboot my phone). A recent Itunes update has not fixed this, nor has the phone update to IOS 4.01.
This is most frustrating as I would generally never have to reboot my MAC. As a workaround, I avoid this problem most of the time by simply using bluetooth only, and always disconnecting the connection from my bluetooth menu if I move locations etc as if I put the mac to sleep to move it without doing this I get the problem.
Anyone else seeing this issue? Anyone have a fix?
Macbook Pro 17" Mac OS X (10.6.4)