Axis movement problem [SOLVED]

I don't know if this is a configuration issue or this thread should be in another area in the forum.

Anyway, my problem is that axis movement starts before another axis has reach its destination. This means for example that there will be a bigger radius in all corners during pocketing and other operations similar to pocketing on the inside of an area.

Let's us use the following as an example

G0 X0Y50
G1 Z-1.0
G1 F800 Y200
G1 F800 X400 // X-axis stars before Y-axis has reach 200
G1 F800 Y0 // Y-axis stars before X-axis has reach 400
G1 F800 X0 X-axis stars before Y-axis has reach 0
G1 F800 Y50 Y-axis stars before X-axis has reach 0
G1 Z30.0 Z-axis stars before Y-axis has reach 50

Is there any one out there who can help me solve this issue?

Tank's for your quick reply, this helped me a lot.