Fatal erro: out of memory

Hi Team,

On the WP dashboard I get the following error:
Fatal error: Out of memory (allocated 77594624) (tried to allocate 1966080 bytes) in /nfs/c09/h02/mnt/127501/domains/tnxt.nl/html/wp-includes/class-simplepie.php on line 5410

The memory_limit is set up to 99M. So that should be enough.
Also when I update it to 256M, I will get the same error.

For your information: We installed the WPMUDEV on a MediaTemple GS hosting.

Do you have a solution?

Thank you in advance!
Stijn