ERROR: mmap() memory failed without memory

We have MongoDB V 1.8.0 running in SUSE Linux Enterprise server version 11.2 (64 Bit). The machine has 64 GB of memory. 

We receive almost ~64GB of data every day and we store each day data into new database. As a backup we store last 5 days data in mongodb.

MongoDB runs fine for couple of days without any issues, after few days it starts to throw ERROR: "mmap failed with out of memory"and the document insert to the database fails. The database would function normally after we restart the mongod instance.

This is the memory usage

>free -m

           total     used      free    shared      buffers     cached

Mem:  64428  64257    171      0             514          57697

 -/+ buffers/cache        6045     58382

Swap:     8191      596       7595

DataBase Stats(): This is almost the same for 5 databases

I am not sure what is causing this error. Can anyone please help me in fixing this Error.

You're using an ancient version and running out of memory.  Smells like a memory leak but I don't think anything can be done other than upgrading to a later supported version.