I am starting to suspect that the libcairo2 dependency comes indirectly from some other library that you have installed. Can you check your system for non-Debian(-sarge) libraries? aptitude search '~i~slibs!~Odebian'
Result: i libmysqlclient15off -mysql client database library
aptitude search '~i~slibs!~A(sarge|stable)'
Result: - returns nothing.
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Helpful?