Sounds like you were using ramzswap only. That won't hold much data (especially with the default config) and so you can run out of virtual memory much earlier, causing the symptoms you describe. Canola and navit (is that stable these days btw?) probably store non-compressible data (images/sounds) which makes the situation worse.

IMO you really do need the swap file as well, just with a lower priority so that the compcache swap is used first while it has any space left.