Comment 0 for bug 115217

It has been reported that sometimes the installer freezes during virtual disk formatting (typically at 33% during System.Virtual.Disk formatting). A pause of 1-15 minutes may be normal, but longer than that is pathological. There are known cases that can cause similar symptoms: a missing HD/controller module will slow down disk I/O to the point that users might think it is jammed, also a pause of 1-15 minutes may be normal. But the problem has been reported also by users with full DMA acceleration that waited several hours.

None of the devs has been able to reproduce the error so far, and even among users that experienced that, it seems that the issue occurs randmoly. NTFS decompression/defragmentation help only occasionally. Reducing the virtual disk size to <= 4GB sometimes seems to help too. See https://wiki.ubuntu.com/WubiGuide under "known issues".