cuabse sx3 + K1.5 editing samples major error

Hello. I use cubase sx3 with kontakt 1.5, and i have a major problem with the system.
The reason that i still use k1 is that i have made so much stuff in it and is has all i need...
The problem occurs when I open the sample in a external editor (soundforge). After editing the sample and closing the file, kontakt should say "sample updated" in the waveform window, right? However this doesn't happen and when i try to close cubse it doesn't respond. Although, if I unload kontakt from the vst intruments rack the program suddently closes and i get a error message from windows about some "access violation".
Regrettably I can't get into details about the error message, I'm not in the studio right now (don't have a internet connection there).
This does not happen if I use the standalone version.
I really need to be able to edit the samples inside cubase, i do sample based music, so i do a lot of cutting and fixing on the sound files...

The sad thing is that started to happen when i bought a new computer recently. I have been using the same software really much on a old computer without any problem at all...

my system is:
Win Xp home edition
cpu: Intel Core 2 duo e6600 2.4 GHz
mainboard: MSI p35 neo-f
ram: 2 gb ddr2 800 MHz
video: Asus Geforce 7600GS 256MB PCI-E.
main hard drive: WD caviar 400 GB sata2
and two IDE drives, seagate and maxtor.