installer fails with partman error code 10

Binary package hint: ubiquity

I am trying to install Ubuntu 8.04 desktop using preseeding. When I run installation with "automatic-ubiquity" kernel parameter, or just run "ubiquity --automatic" from console it fails with "Partman failed with exit code 10".
This happens right after partman scans for partitions. Same thing can be observed on Ubuntu 8.10 Alpha 5.
I tested it on VmWare Server, as well as real pc (both virtual and real pc have linux partitions on hard drive)

How to reproduce the bug:
Boot from Ubuntu 8.04 Desktop CD and either add "automatic-ubiquity" to kernel parameters, or start ubiquity with "--automatic" parameter. Ubiquity fails after timezone selection.