Yeah Both of these two web parts are inherited from
Microsoft.Sharepoint.webpartpages.webpart only!!
and both were given True for allow cross page conncetion parameter at the time
of regestring interface i.e
RegisterInterface("MyParametersOutProviderInterface", //InterfaceName
InterfaceTypes.IParametersOutProvider, //InterfaceType
WebPart.UnlimitedConnections, //MaxConnections
ConnectionRunAt.Server, //RunAtOptions
this, //InterfaceObject
"", //InterfaceClientReference
"Provide Parameters To", //MenuLabel
"Provides a font parameters to a consumer Web Part.", //Description
true); //allowCrossPageConnection
Any idea what went wrong.