ZIP downlad > Fatal error: Allowed memory size exhausted

Description:
When I try to download the whole album as a ZIP (53 pictures, total 140mb) after a couple of minutes the following messages apears:

"Fatal error: Allowed memory size of 50331648 bytes exhausted (tried to allocate 153466981 bytes) in /home/stampfl1/public_html/gallery/util.php on line 1935"

But:
1. On line 1935 I see no possabilitie to change any value like this
2. The funny thing about: In my /temp directory the full ZIP archiv was generated succesfully

Any idea or suggestion?

Cheers,

Roger

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Gallery URL (optional but very useful): http://stampfli.ch/gallery
Gallery version: 1.5.7
Apache version: Apache/2.2.6 (FreeBSD) mod_ssl/2.2.6 OpenSSL/0.9.8e DAV/2
PHP version (don't just say PHP 4, please): 5.1.6
Operating system: Mac OS 10.4.10
Web browser/version (if applicable): Safari 2.0.4