strobe sync problems

I've been using an oly c5050 for a few years and just moved up to a dslr setup. oly e620 & ufl-2 strobe, with f/o cable. I'm experiencing problems which may possibly be due to a lack of experience with the model types, and hope that someone can help.

My images taken in TTL mode are dramatically underexposed and I can't work out why.

The strobe is set to 'rc mode' - the camera is set to 'rc mode' both on channel 1 group A.

The shutter speed does not exceed 1/180th which is the max sync speed.

The rc menu on the camera is set to TTL , +/-0, and the ultra-fast shutter sync option is not activated.

All images at any f/stop are underexposed.

When chosing the TTL option on the 'rc menu' at camera back. The options are 'TTL', Auto' and, I think, 'manual' or maybe 'off'. Anyway, I chose TTL and after the exposure the menu reverts to 'auto' - I can't seem to make it stay in TTL mode.

If anyone has any experience with this setup I would be grateful for some help.

Thanks.

I just bought the UFL-2 to use with an XZ-1 in a PT-050 housing. The instructions are confusing and I've experimented a fair bit. I can get the flash to trigger through the fiber optic cable with RC-on in the XZ-1 flash setting, and in Rc mode on the strobe. But it does not seem to adjust the focus/zoom on the strobe at all, though the focusing light in front blinks. Are there other modes that should be used? Is this a more intelligent apparatus, via Olympus fiber optic cable, than a TTL through the pin connector? Note that the housing for XZ-1 only entertains the fiber optic option, but I've read that it should be as intelligent as a pin connector. I don't want to buy another housing for this camera.