Unable to open 371-06863-100.asm in Creo Parametric 6.0.4.0

I am not sure this is the appropriate forum for your request. The specific assembly and username should not be posted to a public forum. Also, just the fact that the file cannot be opened can result from a bunch of things. You need to investigate more looking at Event Manager or other logs. This is something that should be first handled by your Windchill admin. There is not much the user community can help with currently without more information from your end.