Hi martusi,
Thanks for the post. Let's try to find the problem.
First to all that don't have the ability to read the log file. If you have problems with Joomla or an extension set the Joomla parameter "Error Reporting" to Maximum and you'll see those error messages on the screen. Do not forget to reset it to the original level after the test.
Nice that you installed the mod_gcb_multi3 version of the module. This would have bin my first suggestion.
Does the Cookbook work if you unpublish all "copies" of the modul? Do you have more than 1 modul copy active on each page?
Could you please tell me ALL the module settings for the module (copies of) you use. I'll try to reproduce the problem.
The first message isn't from the module but from the component. Does it still appear after disabling the modul? I'm sure it's corrected in the actual version.
The second message is harder. Your DB is mySql? System Linux?
Do you have a lot of images including hidden images like Lightbox on the pages? This could break the memory size. It may also be an indefinite loop but we can't be sure from which extension it comes.
I also suggest an upgrade to Gary's Cookbook 1.0.6.2. As you now can (have to) use the Joomla installation procedure it's easy. But be sure to read the hints in the Help/Faq before you start. Not only because we only have test systems for this but also if you have plans to migrate to Joomla 1.6+ with the cookbook. This will be the version base to migrate your cookbook data. We are working on the version for J! 1.6+ and only bug fixes will be supported for J! 1.5.
Regards from the colder northern Europe.