DOMPDF will take a lot of memory depending on the HTML you are trying to convert. Propably more than 24M. First try with the highest you can give for memory. Also make sure you have the latest version.
I did both. Increase to 24MB. And I also have latest version. My html has many lines, but I am using bigger html information. Maybe table lines are too much. Lines around 20, and columns around 30.
If this doesn't work, you might have to find another solution for your problem.
Well I am not sure. I look at phpinfo. I move the memory up to 64MB and it worked! thanks!