The scope of validation in ArcIMS Metadata Services only extends to five elements: title, publisher, spatial extent, data theme and resource content type. A default GIS Portal Toolkit (GPT) implementation, on the other hand, requires a much longer list of elements to be present. Due to the differences in the default behavior of the two programs, there are different reasons for why publishing fails in ArcCatalog versus why it fails in the GPT.
ArcCatalog's validation mechanism cannot be modified, whereas the GPT's validation mechanism is fully customizable. If drag-and-drop publishing from ArcCatalog to the GPT is necessary, then the GPT's validation rules must be customized so that metadata documents pass both ArcCatalog and GPT validation. This can be done by customizing the GPT's xml_apply_validation.xslt file. Please see the article in Related Information below for more details.