Suspend to ram occasionally not resuming on HP nc6120 with Ubuntu 8.04

[Frank Breitling]

On resume my HP nc6120 laptop shows a blank screen and also network access via ssh is not possible. The machine does not even answer to ping. So I have to reboot.
This happens not always but on approximately every third resume.
Before I switched to Ubuntu 8.04 (Desktop) I was using Kubuntu 6.10 with my own kernel which had a successful resume rate of 100%.
I already added MODULES_WHITELIST="ipw2200" to the /etc/default/acpi-support but this didn't solve the problem.
I would be very thankful for a solution.