OK there is a glitch on this level where if you got a gold before getting a platinum then you will not be able to get a platinum ever.
Well thats kinda true. You can get a platinum but it will just never save.

There is a simple route and it will get you a platinum every time.

Start by getting rid of the Uplink as it only gets in your view.
Collect the banana just to your right as you start and round the corner.
Collect the banana and take the door on the left.
Collect the third banana and go through into the columns room.
Collect all 5 bananas in here and exit through the other door.
Follow this path and collect the bananas on the way.
Go down the stairs and turn through the left door.
Collect the banana just to you right as you go through the door.
Collect the bananas on the right hand side of the area including the 1 at the top of the 2 steps.
Exit via the central door.
Follow the path collecting the bananas.
As you come into the next area collect the banana just round the corner to your right.
Then run straight ahead collecting the 3 bananas in a line.
Quickly go right across the bridge and collect the banana there.
Turn left and pick up the final 2 bananas.

You should be able to do this with more than 1 second left and in doing so gain a platinum.