The cache in magento , over time , uses up more and more data until the server is crashed.
How do I automatically have magento clear the cache so my server does not crash AGAIN :
In /admin > cache management > auto cache these 3 :
Are you using something different to the base file cache of Magento?
Can you check if the var/cache directory is the cause of the problem? (checking the size of that directory over time)