Camera Labs

Hello I've baught an external flash from ebay that is not from Olympus. The problem I'm havig with it is that when I set the camera to Program mode and use it in low light the camera does not recognise it, in fact when I press the shutter release half way the camera set the shutter speed to 2secs automatically! Is there any setting that I'm missing?

P.S.
This problem does not occur when I use Shutter Priorty mode only!

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Olympus E-5 Olympus E-520
50mm f2.0 Macro 14-54mm f2.8/3.5 II
50-200mm f2.8/3.5 SWD 70-300mm f4/5.6
Hoya Filters CPL, UV, IR, ND8
Olympus FL-50 Digital Flash, x2 Vivitar 285HV x2 Yongnuo YN560
Manfrotto 055XPROB & Lowepro Mini Trekker AW
My fotostream:
http://www.flickr.com/photos/omarbongailas

Is the flash supposed to be fully compatible with the E-520?

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Olympus E620 | 25/2.8 | 50/2 | 12-60 | 14-42 | 14-54 | 40-150 | 70-300
Olympus E-P2 | Panasonic GH2 | 20/1.7 | 14-42 | 14-140
Leica M7 | M9 | 21/4 | 35/1.4 | 50/2.5 | 50/1.5 | 70/2.5 | 90/2
Sony NEX-3 | 16/2.8| 18-55
My FlickR!

When I've asked the seller of ebay he told me that is is fully compatible with the E-520 in fact he had flash for Canon & Nikon etc and I obviosly choose the one compatible with my camera!

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Olympus E-5 Olympus E-520
50mm f2.0 Macro 14-54mm f2.8/3.5 II
50-200mm f2.8/3.5 SWD 70-300mm f4/5.6
Hoya Filters CPL, UV, IR, ND8
Olympus FL-50 Digital Flash, x2 Vivitar 285HV x2 Yongnuo YN560
Manfrotto 055XPROB & Lowepro Mini Trekker AW
My fotostream:
http://www.flickr.com/photos/omarbongailas

That's a stinker ... Sorry, I know less about flash than even the little that I know about cameras. I have the FL36R, and I don't even know how to use all the features on it yet.

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Olympus E620 | 25/2.8 | 50/2 | 12-60 | 14-42 | 14-54 | 40-150 | 70-300
Olympus E-P2 | Panasonic GH2 | 20/1.7 | 14-42 | 14-140
Leica M7 | M9 | 21/4 | 35/1.4 | 50/2.5 | 50/1.5 | 70/2.5 | 90/2
Sony NEX-3 | 16/2.8| 18-55
My FlickR!