Cubase 7.5 - sound issues after reinstallation

Hello everyone,

i have this very strange issue.

First of all:

I bought myself a new computer and since then I witness a strange set of sound problems.

I did not change my Recording setup except the Computer. Everything is still the same (Audio Interface and driver, Monitors, ect). My first switch from Cubase 5 to Cubase 7.5 (also with a new Computer was successful with no problems at all).

I have my Cubase data on an external hdd, so the path to the sound ect remains the same as with my old computer.

The Issues:

When opening an already existing project I witness two very strange sound issues.

Issue 1: Some vocal takes are not played/ have no sound anymore. So when i press play, I can hear the instrumental but not all takes. Since I use comping some takes are hearable and some are not. But when I open the not played take in my pool, I can hear the take.

Issue 2: when pressing the play button the sound is played very confused. At one second I do not hear anything and then 2 seconds later I hear the sound, but more like 5 times faster and then the sound is off again.
First I thought it was a bit oder Khz problem. But the setup is still the same 16 bit 44.1 khz.

Any suggestions?