Buck converter instability (wrong cap size?)

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Hi.
So I have been messing around with this buck converter chip http://www.farnell.com/datasheets/608795.pdf
Sometimes it will be stable, and suddenly, out of the blue, it will act up with the output voltage floating around like crazy (+/- 0.1V).
The datasheet says that it needs 0.1uF caps on input and output, but I can't seem to find any, so I'm using 0.33uF ceramics.
The question is now, can a bigger cap cause trouble? I mean, the bigger cap should fulfil the same task, right?
Also, the input and output caps are 100uF electrolytics instead, but is this a problem with a stable powersupply input?
I'm suspecting the ground loop, but the thing is that it sometimes works, and other times, has it's own will.

Hope you can help here