Problem while updating project using PSI.

Good day.

I have Project Server 2007 installed.

I have some custom code which updates project (add tasks, sets values to enterprise custom fields, etc).

When updating some of the project (only 2 projects with this problem for now) i get PSI exception:

System.Web.Services.Protocols.SoapException: ProjectServerError(s) LastError=GeneralUnhandledException Instructions: Pass this into PSClientError constructor to access all error information
   at Microsoft.Office.Project.Server.WebService.Project.QueueUpdateProject(Guid jobUid, Guid sessionUid, ProjectDataSet dataset, Boolean validateOnly) ---> System.Web.Services.Protocols.SoapException: System.Web.Services.Protocols.SoapException: ProjectServerError(s) LastError=GeneralUnhandledException Instructions: Pass this into PSClientError constructor to access all error information
   at Microsoft.Office.Project.Server.WebService.Project.QueueUpdateProject(Guid jobUid, Guid sessionUid, ProjectDataSet dataset, Boolean validateOnly)
   at System.Web.Services.Protocols.SoapHttpClientProtocol.ReadResponse(SoapClientMessage message, WebResponse response, Stream responseStream, Boolean asyncCall)
   at System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String methodName, Object[] parameters)

In ULS logs i found:

Exception occurred in method Project.QueueUpdateProject Microsoft.Office.Project.Server.Errors.InconsistentInternalStateException: Error in the application.     at Microsoft.Office.Project.Server.Errors.PSError.FailIfFalseTag(ULSTagID ulsID, ULSCat catID, Boolean testCase)     at Microsoft.Office.Project.Server.BusinessLayer.CustomFields.Validate(DataTable customFieldsTable, String entityPrimaryKeyName, DataTable parentTable, Guid entityTypeUid, Guid projectUid, Boolean deleteCFValuesOnModify, Boolean fromWinProj)     at Microsoft.Office.Project.Server.BusinessLayer.CustomFields.ValidateForProject(DataTable customFieldsTable, String entityPrimaryKeyName, DataTable parentTable, Guid entityTypeUid, Guid projectUid, Boolean fromWinProj)     at Microsoft.Office.Project.Server.BusinessLayer.ProjectValidate.ValidateCustomFields(ProjectDataSet dataset, Guid projectUid)     at Microsoft.Office.Project.Server.BusinessLayer.ProjectValidate.ValidateData(Guid projectUid, ProjectDataSet dataset, Boolean isNew)     at Microsoft.Office.Project.Server.BusinessLayer.Project.IsValidData(Guid projectUid, ProjectDataSet dataset, Boolean isNew)     at Microsoft.Office.Project.Server.BusinessLayer.Project.UpdateProjectCore(Guid jobUid, Guid sessionUid, ProjectDataSet dataset, ProjectDataSet deltaDataset, Boolean validateOnly, Guid projectUid, Boolean validate)     at Microsoft.Office.Project.Server.BusinessLayer.Project.UpdateProjectInternal(Guid jobUid, Guid sessionUid, ProjectDataSet dataset, Boolean validateOnly, Boolean validate)     at Microsoft.Office.Project.Server.BusinessLayer.Project.QueueUpdateProject(Guid jobUid, Guid sessionUid, ProjectDataSet dataset, Boolean validateOnly)     at Microsoft.Office.Project.Server.WebService.Project.QueueUpdateProject(Guid jobUid, Guid sessionUid, ProjectDataSet dataset, Boolean validateOnly) 

I tried to look at local custom fields and enterprise custom fields in this projects but with no luck - all seems ok. Projects are published normally from MS Project 2007. And I cannot reproduce this error on my test environment even if i save project as mpp file and transfer it to test server.

Is there any way to fix this problem?

Thank you in advance.

Best regards, Chernobrivets