Environment:
Jenkins version 1.499
Jenkins Subversion Plug-in 1.44
many other plugins.

Description:
Time to time (30% percent of the total builds number) builds stuck.

Notes:
Problem always at the stage of working with svn repository (f.e. check update).
Access to the svn repository from this host is available.
Tasks can not be stopped (till Jenkins full restart)
After Jenkins restart the task is performed

job logs looks like:

• example 1:

  Started by user A
  Building in workspace /home/A/.jenkins/api_functional
  *loader icon*
  

• example 2:

  Started by user B
  Building in workspace /home/A/.jenkins/page_response_status_code
  Reverting /home/A/.jenkins/page_response_status_code/.
  Updating svn://path/qa to revision '2013-01-21T14:23:55.881 +0400'
  *loader icon*
  

threadDump has been attached

Additional information:

Current SCM Polling Activities
There are more SCM polling activities scheduled than handled, so the threads are not keeping up with the demands. Check if your polling is hanging, and/or increase the number of threads if necessary.

The following polling activities are currently in progress:
Project ↓ Running for
API functional 46 min
Page response status code 1 hr 16 min