Dear c0l3s,
I did not find any issues with NAT.
I reported a bug at:
http://bugs.endian.it regarding an issue when using the Anti-Virus with the HTTP Proxy... From what I observed the HAVP process is causing a memory leak.
From the HTTP Proxy Cache Management configuration, it does not seems to offer any control on the cache flushing. I always believed that it is performed automatically on a FIFO basis (First In First Out) and that old entries are overwritten by newer entries when memory reaches the set limit.
Regards,