Blogger importer help needed

I want to import my blogger blog content to wordpress. However it appears always an error message ‘fatal error’: allowed memory size of 268435456 bytes exhausted(tried to allocate 72 bytes) in …./wp-includes/simplepie/parser.php on line 325.

Please can anyone help me? I’m do confused as my hostprovider told me that on their side is everything fine. (my xml importfile is 17 MB

Thanks
Michaela