Memory consumption on iOS

I'm investigating a problem that seems to be related to the memory consumption in Adobe AIR. After about a day of working my application's memory footprint grows from 50Mb to 110Mb, it slows down and eventually crashes at random places with random error codes (I've seen 1090, 1009, 1085, 1069 error codes).

I did some extensive profiling and I'm pretty sure there are no memory leaks in the application itself. What I could see though is that there is a growing number of String objects that are not released even after I click Run Garbage Collector button. Object References window doesn't give much info either. All paths to GC root are empty ("Show all paths to GC roots" setting is checked). All String objects are allocated within my app but they are not stored anywhere. The objects are used to either send data through URLStreamer or recieve data in response. I also use ByteArray in the process to read/compress data. There is just one instance of URLStreamer I use. It is worth mentioning that I send http requests quite often - about couple of times per second.

So it looks like String objects references is the main source of memory consumption. I'm running out of ideas of how to resolve it. The issue seems to be quite serious for my project since it basically can not normally execute for too long.

Any ideas? Or any similar experience with Adobe AIR? Suggestions how to research memory leaks any further since Adobe's profiler appears to be useless? I would greately appreciate any advise.