Memory leakage problem didn't go away for Win XP x64 SP2 (when switching channels or changing settings) for tested DVBViewer versions in range v.4.9 - 5.2. DVB-S2 card is PCI TwinHan 1041 (AzureWave SP-400) with most recent drivers I was able to find from 07.2010: v.1.1.2.700.
The problem description briefly: In about 15 min, all of my 4 Gb of physical memory is filled up (if switching from channel to channel once in about 1-2 min) and Windows hangs up in heavy swapping mode.
Originally I have to blame codecs since, memory is not released when DVBViewer is closed (OS restart is needed). However, recently I have installed wide set of various codecs. And it didn't affect the problem in any way.
Required sys info extraction file is attached as well as some screenshots from SysIntenal util-s.
support.zip