DNS problems

I'm using firmware 3.0.0.4.260.

Once in a while, computers in the network complains about DNS problems and most of the Internet becomes unaccessible, even though some connections do not drop.

When this happens, I check the log file and it's full of these messages:
Nov 28 16:13:57 kernel: VFS: file-max limit 22684 reached
Nov 28 16:13:59 kernel: VFS: file-max limit 22684 reached
Nov 28 16:14:02 kernel: VFS: file-max limit 22684 reached
Nov 28 16:14:05 kernel: VFS: file-max limit 22684 reached
Nov 28 16:14:08 kernel: VFS: file-max limit 22684 reached
Nov 28 16:14:11 kernel: VFS: file-max limit 22684 reached
Nov 28 16:14:14 kernel: VFS: file-max limit 22684 reached
Nov 28 16:14:17 kernel: VFS: file-max limit 22684 reached
Nov 28 16:14:20 kernel: VFS: file-max limit 22684 reached
Nov 28 16:14:24 kernel: VFS: file-max limit 22684 reached
Nov 28 16:14:29 kernel: VFS: file-max limit 22684 reached
Nov 28 16:14:32 kernel: VFS: file-max limit 22684 reached
Nov 28 16:14:38 kernel: VFS: file-max limit 22684 reached
Nov 28 16:14:41 kernel: VFS: file-max limit 22684 reached
Nov 28 16:14:44 kernel: VFS: file-max limit 22684 reached

Does anyone have this same problem or how to fix it?