Gavagai

Recipes 

I just bottled an extract pale ale (with half a pound of crystal malt) and it has a very strong DMS taste. I'm quite confident that this is what the flavor is, as it's something I often taste in pale lagers, but never elsewhere, and has a cooked vegetable type flavor. The flavor is much stronger in the smell than the taste, but is present in both. The only thing I can think of that I did differently is that I added half the extract later than I usually do (though I have been doing late additions all along) and didn't reach a full boil after adding the late addition.

Has anyone else experienced this problem? Are there any other possible causes?

MalFet

Recipes 

I heard somewhere that some metabolic process by some infection organism could cause DMS, but it sounds to me like you've already found your problem. Extract has most of its DMS already boiled off, but if you are particularly sensitive to it I am not surprised to hear that you notice it coming from unboiled extract.

I've never had a problem with DMS from extracts before, but I'm not particularly sensitive to it.