ADD to previous post.
It seems that I have too much users.
This is my case:
I have about 14.000 fake users created with CBJuice.
An auto action add those users to several GJ groups at registration. So I have that every user is auto-subscribed at about 30 groups.
This way I have 30 groups with 14.000 users per group.
If I try to open a group I have a memory size exhausted error.
After deleting 2000 users, now I can see again my user profile, but still with 12.000 users per group I cannot open any group. If group's users stay around 500-6000 users per group, it load with 512MB memory limit.