Hi,
in v1.91,
I was finding
a) some items descriptions were becoming 0 characters and so being omitted from the feed file and
b) debug errors in the cache:
[FONT=Courier New]PHP Warning: htmlentities() [<a href='function.htmlentities'>function.htmlentities</a>]: Invalid multibyte sequence in argument in D:\My Documents\....\tienda\includes\classes\google_base.php on line 276[/FONT]

I found that it was symbols like the TM trademark and copyright that were crashing the google_base_sanita function.

So, in google_base.php
around line 277 look for

PHP Code:
$str = html_entity_decode($str); 
and change it to

PHP Code:
$str = html_entity_decode($str, ENT_QUOTES, 'UTF-8'); 
Otherwise I find this version to work ok.