Screen not resuming after S3 resume

I am running 2.6.0-test6 on a Dell Inspiron 4150 (mainly for the better ACPI support) and ACPI works perfectly out-of-box. However, if I issue
1 or 3 to /proc/acpi/sleep, when I try to resume the screen display does not come back. I am sure the system has resumed correctly though because when I do Ctrl-Alt-Del, the system displays all signs of going for restart and
then restarts and I can ssh in. Do I have to issue a command on resume to bring back the display, and if so how? This happens in both console and XFree86. I have applied the relevant DSDT from the acpi website for the 4150, but it made no difference. Actually I did manage to get the screen to come back from a standby (not a suspend), but immediately after this I tried again and the display wouldn't come back. I tried unloading the radeon.o module, but it made no difference.

The relevant log portion:

----------
PM: Preparing system for suspend
Stopping tasks: =========================|
hdc: start_power_step(step: 0)
hdc: completing PM request, suspend
hda: start_power_step(step: 0)
hda: start_power_step(step: 1)
hda: complete_power_step(step: 1, stat: 50, err: 0)
hda: completing PM request, suspend
PM: Entering state.
Back to C!
PM: Finishing up.
PCI: Setting latency timer of device 0000:00:1f.5 to 64
hda: Wakeup request inited, waiting for !BSY...
hda: start_power_step(step: 1000)
blk: queue c1311c00, I/O limit 4095Mb (mask 0xffffffff)
hda: completing PM request, resume
hdc: Wakeup request inited, waiting for !BSY...
hdc: start_power_step(step: 1000)
hdc: completing PM request, resume
Restarting tasks... done
----------

when resuming from S1.

Any help is much appreciated.

-Si

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