Fatal Error after copying Pro Site to plugins folder

Finally went to install Pro Sites over Supporter. I think the instructions are not very clear. I deleted all the supporter files in the mu-plugins folder. Had to delete all the supporter advertising AND the Upgrades plugin files (this was not in the instructions). I think I have all remnants of Supporter and associated plugins removed.

So, when I FTP the pro-sites plugin files to the plugins folder and then try to Activate the pro-sites plugin, I get this error: Fatal error: Allowed memory size of 67108864 bytes exhausted (tried to allocate 122880 bytes) in /home/golfdawg/public_html/wp-admin/network/menu.php on line 53

Then I can't move anywhere in the admin screen. I have to delete the pro-site files in order to access anything in the admin areas. (I only have 64MB of memory available on our hosting plan).

Any ideas? Thanks.