Crash when loading bigger projects

Dear User,
I am facing the following problem:
I went from Win 7 32 bit to Win 7 64 bit and installed all my plugins and cubase artist 8.0.35 in 64 bit versions. Then I added extra RAM to the system and changed my SSD mode from IDE to AHCI.

This morning I worked on a project with 4 gb RAM and SSD in IDE mode and now after the switch to AHCI and 8 gb installed RAM I get the following crash just before the project is completely loaded:(sorry for the german error log)

Problemereignisname: APPCRASH
Anwendungsname: Cubase8.exe
Anwendungszeitstempel: 5654c8b1
Fehlermodulname: ntdll.dll
Fehlermodulversion: 6.1.7601.19045
Fehlermodulzeitstempel: 56259295
Ausnahmecode: c0000005
Ausnahmeoffset: 00000000000c1220
Betriebsystemversion: 6.1.7601.
Gebietsschema-ID: 1031
Zusatzinformation 1: cc6a
Zusatzinformation 2: cc6a5e2349b7103a96363bdf6521b991
Zusatzinformation 3: d530
Zusatzinformation 4: d530a46fea1c20732c9dbc237ef79c4c

I checked if both RAM sticks are working properly and both seem ok. I went back to IDE mode and still get the error. When I open a project that uses mainly audio tracks and only one VSTi, I don’t get the error. When I open more VSTi’s in this project (so that more than 1 gb of RAM is used by Cubase) I can still work in the project, but when I save it and try to reopen it, I get the crash. I also tried to reinstall Cubase but the problem is still present also with version 8.0.0.

Edit: Today I installed the 32 bit Version and the “big” projects (of course only until 4 gb are needed) are working.

Any ideas???

I am thankful for ideas and troubleshoots.