SQL Server Memory Problem

Hi,

I had come across an issue recently where the SQL server 2008 instance stopped accepting any connections and became unresponsive. I had to restart the SQL server to bring it back.

The bellow error is logged in SQL log. 

Error:

--------------------------------------------------------------------------------------------------------------------------------------

AppDomain 2 (database.dbo[runtime].1) created.

Unsafe assembly 'tldbwin32clientmanagedinterface, version=0.0.0.0, culture=neutral, publickeytoken=null, processorarchitecture=msil' loaded into appdomain 2 (database.dbo[runtime].1).

Failed Virtual Allocate Bytes: FAIL_VIRTUAL_RESERVE 1048576

-------------------------------------------------------------------------------------------------------------------------------------

What does this error mean and how this can be addressed? 

Any help on this appreciated. 

Thanks,

Vipin