That is the primary reason I chose not to use SBCL (Lisp) to implement the game engine I'm building. I really wanted to, but SBCL leaks memory on Windows. When I asked their mailing list about how to fix it, the community was silent. Those two issues make it impractical to use SBCL to develop a product.
Lua is used in games often. It does have GC, with an incremental non-compacting generational GC. If you do get pauses then there are various methods of forcing GC on a regular basis, or just generating less garbage. It works well in practice.
