Perhaps talk to Jointed Rail first as it's their DLC, not official N3V, they have a section in the Payware forum and are usually extremely helpful.
However not actually heard of anyone else with that problem on the pack?
Possibly somehow during the install process the items got opened for edit, happens occasionally, if an EDR has been done or when importing content.
Try right click on each item and revert to original unless it's greyed out, might just clear the problem. Usually even old content is fine so long as its not opened for edit or CCP isn't used on it and you use revert and not commit.
If not.
Most of those errors other than the missing thumbnail container are simple deletes.
For Info:
AssetX is a handy tool that will fix most config errors of that nature and a load more, plus create the thumbnail container and required thumbnail if its missing, bit of a learning curve with it however it save the the need to manually edit.
http://members.optusnet.com.au/~villaump/pevsoft.htm, lot of other very useful stuff for Trainz there as well it's worth having.