I tried this instead:
<cfset main = ImageNew("D:\Inetpub\staffnet_test\hep\bios\#lcase(filename)#")>
<cfset thumb = ImageNew("D:\Inetpub\staffnet_test\hep\bios\thumbs\#lcase(filename)#" )>
<cfset ImageResize(main,"180","")>
<cfset ImageResize(thumb,"90","")>
No error, but no resizing either.
I'm not sure why it wouldn't find the file. It's a Windows machine, so not case sensitive. Let me try to return the path variable names and see what I get. Odd though, because the upload function uses the same variables, and the files upload fine.