Authentication issues on domain computers.

hello, i've been having problem since last week , it's happen several times since. @ random times users lose connection file server (deployed gpo), outlook loses connection exchange, login workstations , servers takes long time. after period of time starts working again if nothing had happened. it's important mention while issue going on workstations , servers don't lose internet , can ping , resolve dns every server on network. discards issue being network connectivity. these aspects we're having trouble authentication based  so has lead me believe issue has our domain controller. have 3 windows 2008 r2 domain controllers, oly 1 being primary dc. have checked logs on 3 of them , there no clue happening. have checked dns on 3 , it's fine. i've checked dfs replication , it's working fine. activated userenvlog on workstation in hopes of finding clue don't understand on log.

i uploaded userenvlog skydrive. here link: http://sdrv.ms/x50heb

i'm clueless happening. don't know else do. please technet community need help!! thanks.

did userenv.log captured during problem? found dc (dc06) was responsive. have checked cpu utilization pdc after logged onto it? if yes, how it? if cpu under high pressure, please try figure out process takes resource , try rid of that.
if cpu utilization not high during problem, please make sure there are gc servers available in domain and check if of domain controllers have same problem (slow logon) during issue, if yes, go network monitor trace helpful.
if no, please try login user on dcs , make user contain domain local groups (this avoid dc contact gcs universal groups) , check result.  can check if there third party password filters installed on domain controllers, password filters, can refer http://blogs.technet.com/b/tristank/archive/2005/07/19/passfilt.aspx for more info.

Windows Server  >  Directory Services