unable to allocate memory for mutex;

[GKoo Ansis]

Dear amavis users, i am randomly receiving this error on one of my 
e-mail servers:

Jun 15 06:47:57 dell amavis[28166]: (!!)TROUBLE in child_init_hook: BDB 
no dbS: unable to allocate memory for mutex; resize mutex
region, . at (eval 82) line 27.
Jun 15 06:47:57 dell amavis[28166]: (!)_DIE: Suicide in child_init_hook: 
BDB no dbS: unable to allocate memory for mutex; resize mutex region, . 
at (eval 82) line 27.

The amavis scanner is blocked and all e-mail remains in the queue. If i 
restart the amavis service everything goes back to normal but after a 
while this error comes back. I haven't found anything online about it.
Any ideas are well received. Thanks.