File Permissions Error using load balancers - asp.net

Question

I have a problem with logging. I have a class I use to log events, in my ASP.net application, to a text file. The class seems to work fine. Complications arise, though, because we are using a load balancer. We run our app on two servers. If one server fails, the load balancer will switch the web application to the other server. I can also direct the browser to specify which server to view the application on.
The problem is that when I go to one server, the application can log just fine. But if i try to switch to the other server, I get this error:
Exception Details: System.UnauthorizedAccessException: Access to the path '\myServer-qa\plantshare\someFolder\myApp\Logs\2012_12_14.txt' is denied.
ASP.NET is not authorized to access the requested resource. Consider
granting access rights to the resource to the ASP.NET request
identity. ASP.NET has a base process identity (typically
{MACHINE}\ASPNET on IIS 5 or Network Service on IIS 6) that is used if
the application is not impersonating. If the application is
impersonating via , the identity will be
the anonymous user (typically IUSR_MACHINENAME) or the authenticated
request user.
To grant ASP.NET access to a file, right-click the file in Explorer,
choose "Properties" and select the Security tab. Click "Add" to add
the appropriate user or group. Highlight the ASP.NET account, and
check the boxes for the desired access.
If i delete the file, which ever server creates it first will be fine but the other will fail. If i check the files permissions only the server that created it will have permission. Is this an issue with my code or IIS? Also, We use windows authentication. Here is the class I use to write:
Imports System.Net
Imports System.IO
Public Class logger
Private Shared _thisInstance As logger
Private Shared InstanceLock As New Object
Private Shared FileLock As New Object
Private _path As String
Public Property path() As String
Get
Return _path
End Get
Set(ByVal value As String)
_path = value
End Set
End Property
Protected Sub New(ByVal path As String)
Me.path = path
End Sub
Public Shared Function GetSingleton(ByVal path As String) As logger
SyncLock InstanceLock
If _thisInstance Is Nothing Then
_thisInstance = New logger(path)
End If
End SyncLock
Return _thisInstance
End Function
Private Function checkDir(ByVal path As String) As Boolean
Dim dir As New DirectoryInfo(path)
Dim exist As Boolean = True
If Not dir.Exists Then
Try
dir.Create()
Catch ex As Exception
exist = False
End Try
End If
Return exist
End Function
Private Function checkFile(ByVal path As String) As Boolean
Dim myFile As New FileInfo(path)
Dim exist As Boolean = True
Dim objWriter As IO.StreamWriter
Dim fs As FileStream
If Not myFile.Exists Then
Try
fs = New FileStream(path, FileMode.CreateNew, FileAccess.ReadWrite, FileShare.ReadWrite)
objWriter = New System.IO.StreamWriter(fs)
objWriter.Close()
objWriter.Dispose()
fs.Close()
fs.Dispose()
Catch ex As Exception
exist = False
Finally
End Try
End If
Return exist
End Function
'updates file
Public Sub Logger(ByVal filePath As String, ByVal Message As String, ByVal title As String, Optional ByVal stkTrace As String = "")
Dim sw As StreamWriter
Dim fs As FileStream
Dim path As String
Dim now As DateTime = DateTime.Now
Dim today As String
today = Date.Now.ToString("yyy/MM/dd")
path = Me.path & today.Replace("/", "_") & ".txt"
If checkFile(path) Then
SyncLock FileLock
fs = New FileStream(path, FileMode.Append)
sw = New StreamWriter(fs)
Try
sw.WriteLine("Title: " & title)
sw.WriteLine("Message: " & Message)
sw.WriteLine("StackTrace: " & stkTrace)
sw.WriteLine("Date/Time: " & now.ToString("yyyy/MM/dd HH:mm:ss"))
sw.WriteLine("================================================")
sw.Flush()
Catch ex As Exception
Throw
Finally
sw.Close()
fs.Close()
sw.Dispose()
fs.Dispose()
End Try
End SyncLock
End If
End Sub
End Class