It's not entirely clear what the cause of this is, but it seems to affect 32-bit installs from the ISO only. There have been a growing number of reports, but not a lot of detailed follow-up feedback. The suggestions are to:
wubi.exe standalone (without any DVD/USB containing Ubuntu present) to allow it to download the diskimage install (which does not have this problem), or...
- Install using the 64-bit media (although this doesn't currently work for the latest 12.04.2 wubi.exe unless you use the patched version here: people.canonical.com/~evand/wubi/precise/wubi-r273-signed.exe)
- Review bug 1182805 and see whether you have any information you can add (see more information on this below)
Other people have found switching to the console and back can get it re-started: Ctrl+Alt+F1 followed by Ctrl+Alt+F7
When Ubuntu freezes you should reboot safely by holding down Alt+PrntScr and then pressing the following keys (pause between each one): R E I S U B
Here is some general advice:
Hard reboots or shutdowns can damage the file systems. In your case, you can run
chkdsk from windows to make sure there is no corruption.
You can drop to a terminal when this happens Ctrl+Alt+F1 and see if there's anything interesting in the logs:
cat /var/log/syslog or zip up your logs and file a new bug or - if suitable - attach to the existing bug mentioned above:
sudo zip -r /host/ubuntu/logs.zip /var/log
That command creates a zip file you can find from Windows in
C:\ubuntu\logs.zip (assuming you installed on
C:. Attach that to your bug report.
If you have a graphics card that requires a closed source driver, you could also try booting with