Thank you for your reply.
Version: PHP Version 5.2.10-2ubuntu6.3
Plugins: No new plugins installed, some upgraded, I deactivated those with no result
Memory: no problems there, about half of memory is still available
load average: 1.65, 1.72, 1.57
Tasks: 106 total, 1 running, 105 sleeping, 0 stopped, 0 zombie
Cpu(s): 18.2%us, 2.2%sy, 0.0%ni, 78.6%id, 0.9%wa, 0.0%hi, 0.1%si, 0.1%st
Mem: 1434588k total, 678508k used, 756080k free, 60864k buffers
Swap: 262136k total, 41440k used, 220696k free, 241500k cached
Also, in other plugins and in the WP editor the boxes are more than one line long (and can sometimes be enlarged with the cursor). The problem only manifests it self in the Atuahalpa options editor.