Error while creating Purchase order in Dynamics AX 2012

Hi friends, 

I have been facing the below error while creating new Purchase order in AX 2012. I don't know why it is happening but after digging more into code it crashed while writing code in IL. Some web services running in this may causing this issue please give me any pointer how can I track this as I don't have much idea web services in AX 2012.

NOTE: This error is coming in only one company and I am able to create PO in other companies. 

Cannot create a record in Purchase orders (PurchTable). Purchase order: COM-0000XX, COM-00XXXX.

The record already exists.

Microsoft.Dynamics.Ax.Xpp.DuplicateKeyException: Exception of type 'Microsoft.Dynamics.Ax.Xpp.DuplicateKeyException' was thrown.

   at Microsoft.Dynamics.Ax.MSIL.Interop.throwException(Int32 ExceptionValue)

   at Microsoft.Dynamics.Ax.MSIL.cqlCursorIL.insert(IntPtr table)

   at Microsoft.Dynamics.Ax.Xpp.Common.doInsert()

   at Dynamics.Ax.Application.PurchTableType.Insert(Boolean _interCompanySilent, Date _accountingDate, Boolean , Boolean ) in PurchTableType.insert.xpp:line 21

   at Dynamics.Ax.Application.PurchTable.Insert(Boolean _interCompanySilent, Date _accountingDate, Boolean , Boolean ) in PurchTable.insert.xpp:line 7

   at Dynamics.Ax.Application.PurchTable.@Insert(Boolean _interCompanySilent, Boolean )

   at Dynamics.Ax.Application.PurchTable.Insert(Boolean _interCompanySilent)

   at Dynamics.Ax.Application.PurchCreateOrderForm.writeOnServer(Object[] _params) in PurchCreateOrderForm.writeOnServer.xpp:line 25

   at PurchCreateOrderForm::writeOnServer(Object[] )

   at Microsoft.Dynamics.Ax.Xpp.ReflectionCallHelper.MakeStaticCall(Type type, String MethodName, Object[] parameters)

   at Dynamics.Ax.Application.SysDictClass.invokeStaticMethod(Object[] _params) in SysDictClass.invokeStaticMethod.xpp:line 26

   at SysDictClass::invokeStaticMethod(Object[] )

   at Microsoft.Dynamics.Ax.Xpp.ReflectionCallHelper.MakeStaticCall(Type type, String MethodName, Object[] parameters)

   at Microsoft.Dynamics.Ax.Xpp.PredefinedFunctions.runAsInvoke(String className, String staticMethodName, Object[] parms, Object[]& exportInfolog)