Comment 51 for bug 998156

Seb, in any application with GTK printing dialog try to print with a custom paper size:

Run the command

cupsctl LogLevel=debug

File/Print, in dialog select printer on "General" tab, switch to "Page Setup" tab, click on paper size drop down and choose "Manage Custom Sizes ...". Create a custom paper size. Now choose the newly created custom size and print.

In /var/log/cups/error_log You will find a line like

D [13/Jul/2012:19:24:49 +0200] [Job 626] argv[5]="InputSlot=Default PageSize=Custom.Custom.595.28x841.89 Duplex=None PrintoutMode=Normal PrinterResolution=FromPrintoutMode number-up=1 job-uuid=urn:uuid:bd2f3351-a345-3abb-63d9-ea13d11a8f39 job-originating-host-name=localhost time-at-creation=1342200218 time-at-processing=1342200289"

Note the "PageSize=Custom.Custom.595.28x841.89" in the line.

For some programs (like Firefox for some users) it can even happen with regular paper sizes, but with custom sizes it occurs for sure.

I have tested with Thunderbird on up-to-date Precise now and reproduced it as described above.