I have been having the same issue with my tools too, but not as extreme. I have a relatively new, regularly calibrated hydrometer, and a digital refractometer. I always let the sample cool to between 60-70 before using either of them. I experience difference more like what AJ had mentioned, after conversion to gravity, they can be off by 5 points max (this is for wort, not beer). I have also found that the range of how far it is off varies with OG and color, but I need more data points to make any statements about how. As AJ mentioned, the types of sugars meant to be measured by the instrument is important. When I had purchased my digital refractometer, while browsing around there were a lot of specific applications for them. For instance, I saw one made for wine, maple syrup, honey, nectar... Whether or not the differences are hugely substantial, I am not certain, but I would imagine it could have a result of the magnitude of which you are seeing.
As for fermenting beer, morebeer had a excel sheet with a built in formula that I use to monitor my fermentations with my refractometer readings. In the end, the mismatch can be a bit more extreme, but still within 6 or 7 points.
I would suggest borrowing another hydrometer and seeing how it compares to your own. You also may want to make a few standard calibrations, not just water, but a standard sucrose solution or two, and see how they fit.