Well, you probably already know about the linux-wlan mailing list:
http://lists.linux-wlan.com
You can google for your error messages by entering:
site:lists.linux-wlan.com Tx attempt prior to association
on the search params. (are you certain you're config
is for ad-hoc, not managed/infrastructure?)
I also suspect you've got a fairly simple routing error, which is why I
asked about the output from the commands I mentioned.
(Destination Host Unreachable gives that away). You might
have two interfaces trying to share the same subnet, but I
can't tell. That can be done, but requires extra effort.
If this is not a USB device, you may want to check into
your firmware versions, they may be old, and new firmware often
fixes things. And, again if not USB, there are (at least) two
other drivers to try: hostap and orinoco.
HTH,
-bbeers