32bit pv-grub won't boot

I've built a custom 32-bit kernel, which I'm trying to boot using pv-grub-x86_32, but something's not right.

When I try booting, the dashboard displays a largely unhelpful error ("Linode failed to boot for unknown reason."). logview from LISH is slightly more illuminating, but I'm still at a loss:

Showing last 100 lines from current boot
-----------------------------------------
Xen Minimal OS!
start_info:   0xacc000
  nr_pages:   368640  shared_inf: cf1f1000
  pt_base:    0xacf000  mod_start:  0x0
  mod_len:    0
  flags:      0x0
  cmd_line:   (hd0)/boot/grub/menu.lst
  stack:      0x943780-0x963780
MM: Init
  _text:        0x0
  _etext:       0x5f0ca
  _erodata:     0x73000
  _edata:       0x786d4
  stack start:  0x943780
  _end:         0x963d14
  start_pfn:    adb
  max_pfn:      5a000
Mapping memory range 0xc00000 - 0x5a000000
setting 0x0-0x73000 readonly
skipped 0x1000
MM: Initialise page allocator for da6000(da6000)-0(5a000000)
MM: done
Demand map pfns at 5a001000-da001000.
Heap resides at da002000-1a002000.
Initialising timer interface
Initialising console ... done.
gnttab_table mapped at 0x5a001000.
Initialising scheduler
Heap exhausted: 0xda002000 + 480 = 0xda002480 > 0x1a002000
Heap exhausted: 0xda002000 + b80 = 0xda002b80 > 0x1a002000
Page fault at linear address 0x4, eip 0x519fd, regs 0x95fea8, sp 0x77da0, our_sp 0x95fe88, code 2
Page fault in pagetable walk (access to invalid memory?).

I tried moving menu.lst/grub.conf out of the way in hopes of getting a grub prompt; no joy, same result. This implies some more fundamental problem than a bad kernel or me fat-fingering the configuration.

Just for completeness, I then tried booting pv-grub-x86_64. Oddly enough, this works, in so much as it actually boots to a grub prompt. I can even point it at my kernel (though of course it won't actually boot since the kernel is 32bit).

Ideas please, anyone?

Thanks.