Howdy eandp,
I would love to help you with this. When you see an Allowed Memory error like that it typically means your database/website is growing, and needs a little more power from the server to handle it. Once you get enough comments or posts (which include events) the website can start needing more memory than it currently has.
The good news is most hosting providers allow you to change the memory limit by editing your configĀ file. Right now yours is likely set to 64MB or so. You might try changing it to 128MB. You will have to ask your hosting provider how you can increase the memory limit, as it varies from host to host.
Knowing that, are you able to get the config file changed and thus make the server handle the size of your website?
Cheers!
– Brook