OK, embarrasing question. I've been riding off road reasonably competently for 20 years, inc a bit of racing here and there. I've just moved from a hardtail onto my first FS bike and am having a problem riding through dips - little dips in the track, dried out puddles, etc. Usually, on my Zaskar (with 100mm forks) I just stand up out of the saddle, get my weight back a little and let the bike just flow through the dip with my arms and legs bending to let the bike do all the work.
I'm now finding on my Spesh FSR (120mm forks) like I'm about to go over the bars whenever the front wheel drops into a dip - like the front wheel sinks down, stalls and doesn't fly out the other side like I'm used to. I've actually ended up completely over the bars in a heap on one occasion and embarrassingly out of shape, feet out of the pedals in preparation on a number of others - this is mostly on trails I've been riding for years too.
The time I ended up over the bars was just dropping down a 6inch step onto sand, the front wheel just stopped dead and pitched me over. I've flown past that a hundred times before on my HT without even thinking about it.
WTF?! Front forks too soft perhaps? Geometry related?