Firstly, no theistic philosopher or apologist that I am aware of has ever maintained that whatever exists needs a cause, but rather, whatever* begins *to exist needs a cause. This is patently obvious to everyone (outside of insane asylums and graduate schools), and thus The Sound of Music reminds us, “nothing comes from nothing, nothing ever could.”
Secondly, the “age old problem” which you refer to, does not seem to me to be all that problematic. Theists do not believe that God created everything; rather, they believe that God created everything other than himself. God is by definition eternal and uncreated, a metaphysically necessary being whose non-existence is impossible.
Matt Fradd