Need help with "Image Processor: Error executing the action Load"

Here is the link to my website:
www.progolfhq.com/tournaments_add.asp

Below is the error message when you go to:
www.progolfhq.com/tournaments_add.asp

Server Error in '/' Application.
Unable to serialize the session state. Please note that non-serializable objects or MarshalByRef objects are not permitted when session state mode is 'StateServer' or 'SQLServer'.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Web.HttpException: Unable to serialize the session state. Please note that non-serializable objects or MarshalByRef objects are not permitted when session state mode is 'StateServer' or 'SQLServer'.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[SerializationException: The type DMXzone.ImageProcessor.ImageProcessor in Assembly DMXzone.ImageProcessor, Version=2.5.4.0, Culture=neutral, PublicKeyToken=671245a938f3d790 is not marked as serializable.]
System.Runtime.Serialization.FormatterServices.InternalGetSerializableMembers(RuntimeType type, Boolean excludeNonSerializable) +868
System.Runtime.Serialization.FormatterServices.GetSerializableMembers(Type type, StreamingContext context) +300
System.Runtime.Serialization.Formatters.Binary.WriteObjectInfo.InitMemberInfo() +103
System.Runtime.Serialization.Formatters.Binary.WriteObjectInfo.InitSerialize(Object obj, ISurrogateSelector surrogateSelector, StreamingContext context, SerObjectInfoInit serObjectInfoInit, IFormatterConverter converter) +511
System.Runtime.Serialization.Formatters.Binary.WriteObjectInfo.Serialize(Object obj, ISurrogateSelector surrogateSelector, StreamingContext context, SerObjectInfoInit serObjectInfoInit, IFormatterConverter converter) +48
System.Runtime.Serialization.Formatters.Binary.ObjectWriter.Serialize(Object graph, Header[] inHeaders, __BinaryWriter serWriter, Boolean fCheck) +683
System.Runtime.Serialization.Formatters.Binary.BinaryFormatter.Serialize(Stream serializationStream, Object graph, Header[] headers, Boolean fCheck) +136
System.Web.Util.AltSerialization.WriteValueToStream(Object value, BinaryWriter writer) +1621

[HttpException (0x80004005): Unable to serialize the session state. Please note that non-serializable objects or MarshalByRef objects are not permitted when session state mode is 'StateServer' or 'SQLServer'.]
System.Web.Util.AltSerialization.WriteValueToStream(Object value, BinaryWriter writer) +1711
System.Web.SessionState.SessionDictionary.Serialize(BinaryWriter writer) +150
System.Web.SessionState.StateClientManager.Serialize(SessionStateItem item, Stream stream) +146
System.Web.SessionState.OutOfProcStateClientManager.System.Web.SessionState.IStateClientManager.Set(String id, SessionStateItem item, Boolean inStorage) +121
System.Web.SessionState.SessionStateModule.OnReleaseState(Object source, EventArgs eventArgs) +465
System.Web.SyncEventExecutionStep.System.Web.HttpApplication+IExecutionStep.Execute() +60
System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +87

Also; I'm using the hosting company called IXWEB hosting; they said the following; "I am sorry for the problem you have faced, but unfortunately structure of application you are using is not quite clear. The error that you get on site now is related to ASP.NET session settings, but as I can see you are using Classic ASP code and do not have ASP.NET files. However if ASP.NET is disabled on Control panel -> Web options tab -> ASPNET field, then another error on your site is shown. Could you please update this ticket and explain us how your application is configured and if you are using ASP.NET component for Classic ASP code and how it is implemented in order we can check if server configuration should be adjusted. Thank you for your patience and kind understanding."

I'm have the SAME PROBLEM!

My site was working fine until a few days ago, also. I, too, have IXWeb as a host. But I've had them for a while. When I came across the issue the first time (2 months ago), IXWeb upgraded the server to ASP.NET v4 and it seemed to work. Now, for some reason, it is back to giving the old error. I asked IXWeb and they confirm that I am still using ASP.NET v4 so that's not changed.

Can you please shed more light on this? Thanks!