I fixed the problem!
If anyone is interested, i will write a quick report.
Making timevector contiguous: delete old mobiledev and create a new one. I dont know why this problem occurs, but this is a simple fix.
Receive logged data completly: Matlab Mobile needs quite some time to postprocess the logged data. Therefore you have to wait some time until the log-functions return vectors with the appropiate length. I automated this process with the code showing below:
t_Accel_old = 0;
%get data from mobiledev and save in var
[Accel, t_Accel] = accellog(m);
t_Accel_old = t_Accel;
I hope my explanation is helpful and saves someone some time.