What special considerations exist for putting a module inside a lib?

I have a module which works fine when included as sourse code in various projects but when I try to put it in a lib file and add the lib file to the source files I get various link errors which were not there before.

The Mod file has been copied to the INCLUDE directory.

in one case only two routines (out of a set of very large number in the module) are picked on, as being unresolved and are being looked for by different decoartions

LNK2001: unresolved external symbol _AUTOARRAYS_mp_AA_SORT@4
&
LNK2001: unresolved external symbol _AA_RESET@4

In another case I get the ol' mysterious:
arning LNK4098: defaultlib "libc.lib" conflicts with use of other libs; use /NODEFAULTLIB:library

Any hints will be appreciated.
Tx,
TimH