Hey, just installed both the emember and estore plugin, receiving the same error message. Thanks for the help!
Also, just to note, I believe my server is php5.
one last thing, I believe it is affecting the way that estore and emember plugins integrate, when i do a test purchase using paypal sandbox, everything works properly up to the customer being added as a member in emember ( a customer is created in the estore side) and the customer getting an email about registration. I can email more details if necessary.