ldconfig not working anymore?

hey, there, I am under UBUNTU. I usually put a rarely used shared library into a local directory, and put the local directory into the file /etc/ld.conf.so.d/rarely.conf, and then run ldconfig, and the shared library works. However today, it stopped working, and even worse, other local shared libraries, which used to work, also stop working. The complaint is identical:
ld: cannot find -lmylib

I have no clue how to figure out where is the problem, except suspecting that ldconfig. please share with me you idea. Thanks.

Do you see anything suspicious when you do:

Code:

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$ LD_DEBUG=all foo

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Where foo is a program which doesn't dynamically link properly anymore?