Fixed guys. At the end I had to buy the new product Dual Perfect that gives me more memory.
Thanks 4 your help!!
I have just talked to 1&1. They told me that the memory tricks don’t work and that I am not allowed to do that. And if I want to solve that problem I can change to a better product with more memory, the new and more expensive ones have 60 and 90MB.
The thing is that I have no clue how much memory I need… I want to install buddypress and create some profiles. The web is going to be a city guide for Madrid with reviews and photos.
Do you know if 60 MB or 90MB is enough?? Any other hosting supporting WordPress, MySQL databases, more memory and a reasobale price?
Thanks
Thank you aces, I’ll talk to them anyway and shout a little. 
increased memory in the wp-config.php, I included this line at the beginning of the php
`define (‘WP_MEMORY_LIMIT’, ‘256M’);`
also tried with 500MB and nothing happens…the errors still occur. 
(
my host is 1&1, I got the pack with 2 domains and 5 databases
