I myself would love to see evidence of this too, as traditionally organics are low in nitrogen, so how these low levels could possibly become toxic would interest me.
When I use organics I often supplement with nitrogen heavy inorganics. Such as ammonium sulfate (speaking of ammonia!)

Shameless bump.....was still hoping I might entice Al to take a stab at this question. :)

When I had a question for Al(tapla), I emailed him direct and he gracious answered quickly. Al

Good idea.

I decided to look into this and it certainly is possible. Two causes for it, lack of bacteria and fertilizers with ammoniacal nitrogen. If you can avoid these fertilizers, you shouldn't have a problem. I know many like to keep fertilizing during the winter. I myself do not. I have heard the reasons why, but my belief is the plants can only store so much nitrogen, and it doesn't take much for the tanks to be full and soon the roots are a burning. Heck I don't even water cacti much in the winter, let alone fertilize. One exception is Christmas and Easter type cacti, and similar succulents do flower in the winter so require fertilizer. These are also very sensitive to salts.
As far as roses, remember organics take time to break down, at least 2 weeks to a month or more, so you want to fertilize before they start growing. Plus bacteria usually do not die off completely in ground, even in the winter. I usually put down organics in March for April growth.
Anyway organic can cause problems in the winter, and switching to soluble makes some sense to me. Most of my plants are dormant and the soil is rich enough, I don't fertilize, but to each his own. If it works don't fix it.
Low doses is not going to hurt anything as long as you don't have build up, and that is near impossible with soluble fertilizers. Too much could be a problem.
Some plants though like most cacti, you could certainly kill the plant if you fertilize while dormant, even in small doses.
Normal house plants could even benefit from winter fertilizers. Again to me soil, fertilizer, light, all depend on what you are growing. Plants differ so much.
I water my cacti a few ounces every month and that is it.
I still have about 40 gallons of rainwater, so all set for the winter. I keep it in my garage.

On another subject I finally found a good substitute for granite. Yeah! Horticultural cork! Acts like granite, doesn't absorb any water. It won't last like granite, but will last longer than pine bark. Super light weight, and that is exactly what I needed! Speaking of which Monterey Pine Bark lasts a lot longer than any other type of pine bark. Awesome stuff! I found a good mix at last! Cork, Monterey Pine Bark, and pumice.
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Drew, can you post up a picture of the cork and how it looks in the mix?

Cork is just another kind of bark. I would not consider it as a substitute for granite. Like Perlite, I would expect it to tend to migrate to the top of the mix. Getting the pieces the right size for the mix could also be a problem. Al