I am having this issue too on a shared web hosting environment. But, only have 1 blog per app_pool
The host I am using only allows up to 100mb for the app_pool before it recycles the app_pool meaning it stops the app_pool giving the website an
500 Server error which causes it to go down until you restart the app_pool.
I am using BE 188.8.131.52
The website have over 100 posts using xml for the database.
The website I am talking about is this one:
Some times my other sites go down too
like this one
Both are using xml databases