[TYPO3] Fatal error: Allowed memory size

[Xatu Cans]

Hi, I've a Typo3 4.1.1 site and it worked fine since two days ago, when it 
started to show this error:

Fatal error: Allowed memory size of 8388608 bytes exhausted (tried to 
allocate 311296 bytes) in 
/home/argitron/public_html/agenda21/typo3_src/typo3/sysext/cms/tslib/class.tslib_content.php 
on line 1059

The error  always happends in Frontend, but I can accede to Backend and 
Install Tool, but there are several modules of the backend that show the 
same error, for example: the ext manager, the db check module... I´ve 
acceded to the install tool I've seen the memory_limit is only 8MB, so I 
think the problem is here, and my question is if is there any way to change 
this parameter without updating the php.ini, because  haven't my site in my 
own server and I can't change it