Unhandled Execution Error Oracle.DataAccess.Client.OracleException:

Hi,Since i have installed windows 8.1 on my computer i have been facing this issue.
Not able to connect to oracle using oracle.dataaccess.client.
connection to oracle through sqlplus ... ok
following is the trace :

[OracleException] Oracle.DataAccess.Client.OracleException.HandleErrorHelper(Int32 errCode, OracleConnection conn, IntPtr opsErrCtx, OpoSqlValCtx* pOpoSqlValCtx, Object src, String procedure) +333 Oracle.DataAccess.Client.OracleException.HandleError(Int32 errCode, OracleConnection conn, IntPtr opsErrCtx, Object src) +63 Oracle.DataAccess.Client.OracleConnection.Open() +6538 ICWAI.dbErrorLogging.HandleException(Exception ex) +1571 ICWAI.dbErrorLogging.LogError(Exception oEx) +186 ICWAI.IEPS.DBAccess.ExecuteReader(String commandtext) in D:\Mohan\Projects\IEPS_DEC\IEPSWAP\AppCode\DAL\DBAccess.vb:55 ICWAI.IEPS.dalTABIEmployees.chkValidUser(clsTABIEmployees objATSUsers, String branchCode) in D:\Mohan\Projects\I ...