VoipSwitch retail module(IPIVR)

We have recently started using retail version of VPS. the maximum concurrent calls we could achieve were 60. the softswitch crashed several times during the last two moths. VPS technical team is trying to fix the bugs but so far they are not successful in that. we have reduced the load on VPS now and it is runing stable at arround 50 concurrent calls except one problem which we are observing. voip box shows pending tasks more than that of voipswitch. once we reset both voipbox and voipswitch pending tasks get equal initially but within next three to four days voipbox shows 150 pending tasks and voipswitch shows 50-60. this scenario starts consuming a lot of CPU resources (approximately 70%). in order to avoid possible CPU unstability under continuous high usage we need to restart the whole programs.

is there any body who has acgieved more than 100 calls on voipswitch in retail(calling card operations) scenario????

thanks
Sheheryar