[linux-lvm] Installation fails if VG is exported

[Misc Things]

Hello,
 i guess i'm doing smth very stupid, but... Here is the story:
 i decided to migrate to RH6 ( SL6). I run pretty old box ( 6 yo,
AST160 ASPIRE) with recently added WD1.5 TB ( i doubt it makes any
difference, but .. ).
System has a few VGs ( LVM2) created and enabled.
I'm a bit paranoid to lose my data during installation - i followed
the LVM's FAQ (http://tldp.org/HOWTO/LVM-HOWTO/recipemovevgtonewsys.html).
Here are the steps i took and the results:
1. umount ;
2.  vgchange -ay
3. vgexport
4. i commented out the VG in /etc/fstab ( just in case ).
reboot - FS is not mounted, VG is inactive - so far everything as expected.

reboot and load network installation, default values are picked up on
the GUI installer's screen.
During the HDs checking phase, anaconda terminates with the message "
unalbe to activate exported VG".
I googled around with not much success. The only similar issue was
closed in2007 (https://bugzilla.redhat.com/show_bug.cgi?id=191879)

Please advise.
Andrew