Can't access auto reply in OWA - Get Unexpected error

When our user try to access the "Auto reply" page in OWA they get the following message.
I'll try to translate it.

Unexpected error
An error has occurred and your request could not be finished.
Try again.


In the event log i get the following error.
Event ID: 4
Source: MSExchange control panel

(i'll try to translate it, translation in bold and parentheses)
Current user: 'DOMAIN\user'
Request for URL 'https://mail.domain.se/ecp/default.aspx?rfr=owa&p=Organize/AutomaticReplies.slab' failed with the following error:
System.TypeInitializationException: Ett undantagsfel uppstod för typinitieraren för Microsoft.Exchange.Configuration.TenantMonitoring.TenantMonitor. ---> System.FormatException: Indatasträngen hade ett felaktigt format.
(System.TypeInitializationException: An exeptionerror occurred for type initiator for Microsoft.Exchange.Configuration.TenantMonitoring.TenantMonitor. ---> System.FormatException: Indata string had wrong format.)
   vid System.Number.StringToNumber(String str, NumberStyles options, NumberBuffer& number, NumberFormatInfo info, Boolean parseDecimal)
   vid System.Number.ParseInt32(String s, NumberStyles style, NumberFormatInfo info)
   vid System.Diagnostics.PerformanceCounterLib.GetStringTable(Boolean isHelp)
   vid System.Diagnostics.PerformanceCounterLib.get_NameTable()
   vid System.Diagnostics.PerformanceCounterLib.get_CategoryTable()
   vid System.Diagnostics.PerformanceCounterLib.CategoryExists(String machine, String category)
   vid System.Diagnostics.PerformanceCounterCategory.Exists(String categoryName, String machineName)
   vid Microsoft.Exchange.Configuration.TenantMonitoring.TenantMonitor..cctor()
   --- Slut på stackspårning för interna undantag ---
  (---End of stack trace for internal exeptions---)
   vid Microsoft.Exchange.Configuration.TenantMonitoring.TenantMonitor.LogActivity(CounterType counterType, String organizationName)
   vid Microsoft.Exchange.Management.ControlPanel.RbacContext.CreateSession()
   vid Microsoft.Exchange.Management.ControlPanel.RbacSettings.CreateSession()
   vid Microsoft.Exchange.Management.ControlPanel.AuthenticationSettings..ctor(HttpContext context)
   vid Microsoft.Exchange.Management.ControlPanel.RbacModule.Application_PostAuthenticateRequest(Object sender, EventArgs e)
   vid System.Web.HttpApplication.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   vid System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)
System.FormatException: Indatasträngen hade ett felaktigt format.
(System.FormatException: indata string had wrong format.)
   vid System.Number.StringToNumber(String str, NumberStyles options, NumberBuffer& number, NumberFormatInfo info, Boolean parseDecimal)
   vid System.Number.ParseInt32(String s, NumberStyles style, NumberFormatInfo info)
   vid System.Diagnostics.PerformanceCounterLib.GetStringTable(Boolean isHelp)
   vid System.Diagnostics.PerformanceCounterLib.get_NameTable()
   vid System.Diagnostics.PerformanceCounterLib.get_CategoryTable()
   vid System.Diagnostics.PerformanceCounterLib.CategoryExists(String machine, String category)
   vid System.Diagnostics.PerformanceCounterCategory.Exists(String categoryName, String machineName)
   vid Microsoft.Exchange.Configuration.TenantMonitoring.TenantMonitor..cctor()
(vid = at)


And when running Get-WebServicesVirtualDirectory | FL i get:
RunspaceId: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
CertificateAuthentication:
InternalNLBBypassUrl: https://mail.domain.se/ews/exchange.asmx
GzipLevel: High
Name: EWS (Default Web Site)
InternalAuthenticationMethods: {Ntlm, WindowsIntegrated, WSSecurity}
ExternalAuthenticationMethods: {Ntlm, WindowsIntegrated, WSSecurity}
LiveIdSpNegoAuthentication: False
WSSecurityAuthentication: True
LiveIdBasicAuthentication: False
BasicAuthentication: False
DigestAuthentication: False
WindowsAuthentication: True
MetabasePath: IIS://MAIL.DOMAIN.SE/W3SVC/1/ROOT/EWS
Path: C:\Program Files\Microsoft\Exchange Server\V14\ClientAccess\exchweb\EWS
ExtendedProtectionTokenChecking: None
ExtendedProtectionFlags: {}
ExtendedProtectionSPNList: {}
Server: MAIL
InternalUrl: https://mail.domain.se/EWS/Exchange.asmx
ExternalUrl: https://mail.domain.se/ews/exchange.asmx
AdminDisplayName:
ExchangeVersion: 0.10 (14.0.100.0)
DistinguishedName: CN=EWS (Default Web Site),CN=HTTP,CN=Protocols,CN=MAIL,CN=Servers,CN=Exchange Administrative Group (FYDIBOHF23SPDLT),CN=Administrative Groups,CN=First Organization,CN=Microsoft Exchange,CN=Services,CN=Configuration,DC=DOMAIN,DC=SE
Identity: MAIL\EWS (Default Web Site)
Guid: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
ObjectCategory: DOMAIN.SE/Configuration/Schema/ms-Exch-Web-Services-Virtual-Directory
ObjectClass: {top, msExchVirtualDirectory, msExchWebServicesVirtualDirectory}
WhenChanged: 2011-04-08 14:25:41
WhenCreated: 2011-04-08 14:25:41
WhenChangedUTC: 2011-04-08 12:25:41
WhenCreatedUTC: 2011-04-08 12:25:41
OrganizationId:
OriginatingServer: DC.DOMAIN.SE
IsValid: True

I really hope that someone can help me with this because the users frequently uses the auto reply.