[Touch Pro, Fuze General] hyachts:
I'm having a similar problem, but no amount of checking, unchecking and soft resetting will get me back to the HTC pop-up menu about what type of connection I want. I can force several different behaviors using the USB to PC settings page:

1. "Ask me first" checked, ASync radio button selected, "Enable faster connections" checked: the phone connects to my PC as a network adapter (1692540.2.xxx subnet, which I think is the standard for the Async faster connection mode), I see no activity on the phone at all (except normal "on charge" stuff, and once the PC gets an IP address on the phone's LAN I see no activity on the PC. Async does not sync, although if I open it on the phone it appears to be trying to. Async on the PC never recognizes the device

2. "Ask me first" checked, ASync radio button selected, "Enable faster connections" un-checked: Async connects and syncs as expected, still no HTC pop-up on phone, but I do see the Async USB "host authenticated" and so on messages on the phone

3. "Ask me first" un-checked, ASync radio button selected, "Enable faster connections" un-checked or checked: Internet sharing comes up automatically when I connect the USB cable. Sometimes it sets itself up and connects successfully, sometimes not - I haven't been able to detect a pattern. Shutting down ICS does not make Async start working, however

4. "Ask me first" un-checked or checked, Disk Drive button selected:

Card comes up as removable storage on PC, no HTC pop-up no matter what

The only thing I can think of that might have affected this is that I tried using WMWifiRouter's 3G to USB mode a few weeks ago. I can't be sure that's when I started having this problem, but it was around that time. So... anyone have any thoughts? It seems to me that ICS is somehow now trying to launch every time.

Note that before a few weeks ago the USB connection was working exactly as expected - I got the HTC pop-up menu and could select a type of connection, I could turn the menu on and off using the "ask me first" setting or the "remember this" in the pop-up.

EDIT: So I fixed the pop-up issue. Went into the registry and switched the key HKLM\Software\OEM\USBtoPC\DisablePopUpUI from 0 to 1 (which should disable the pop-up that's already disabled...). Plugged in my USB cable and, as I'd expect, no pop up. Switched that key back to 0 and, whaddyaknow, my pop-up is back. Your guess is as good as mine about why the phone wasn't recognizing that switch. So that part's fixed - now I just have to figure out why my "advanced network" Async connection stopped working. I realize that's a whole issue in and of itself.

EDIT2: Now Async with advanced network is working again. I changed the reg key in HKLM\Software\OEM\USBtoPC\EnableAdvanceChecked from 0 to 1 (although is, also, appears to be changing with the checking and un-checking of the box in settings, so I'm not sue why doing it manually changes anything...) The only other thing I can come up with is that previously when ICS was coming up automatically it was causing the network adapters on the phone some confusion with IPs so the computer couldn't see the phone on the virtual network adapter set up for sync. That's a real shot in the dark, but I'm happy to be back in business regardless...