I recently installed Lubuntu onto a 160Gb HDD, alongside Windows, which is the first two partitions (System Reserved/C:). The installation completed just fine, with no errors. It then rebooted into GRUB. I tried to boot (L)Ubuntu and I got a message similar to this:
attempted to read/write outside of hd0
press any key to continue...
Using the normal Ubuntu menu option, pressing any key causes the system to hang. However, pressing any key on the recovery mode (under Advanced Options for Ubuntu) brings me to a low-res kernel panic (lower resolution than Grub).
Booting into Windows works just fine.
I apologise if this is an ametuer mistake, but I have never had to diagnose bootloader problems in the past (Windows XP/Ubuntu a few years ago, on an older laptop, worked just fine)
Windows was installed first.
Linux - strangely - shows up as sda5/sda6 (from the live CD) when Windows only shows four partitions on the disk.