Hmm thats seems like it could become annoying... maybe the circuitry in the lens is bad, but that seems highly unlikely for an L lens.
Is it causing any problems with TTL and flash output?

the EF-S 17-55mm f/2.8 IS is not an L-series lens.

And yeah, it would mess with an external flash's zoom head setting, but it shouldn't screw with ETTL metering unless the distance information is being reported incorrectly as well. Unfortunately there is no way to check this, as it's not stored in the EXIF data, IIRC.

I'm assuming you've cleaned your contacts already, yah?

(also, bestest avatar)

Indeed I have. This has been happening for about two months, now, I realised, last night. Obviously not a huge issue, since I went so long without noticing, but it would be nice if my lens worked properly. :(

I'm not too familiar with how lenses determine what focal length they're at, but I can imagine that it's likely measuring resistance between two points, 17mm being the least resistance (closest) and 55mm being the most (furthest). If that IS the case, then likely something is dirty or damaged on that piece.

I did a bit of searching, and it seems that the repair is less than $100 at http://www.precisioncamera.com/ (including shipping both ways). Might be worth a shot!

Camera firmware update perhaps? Although I think the 7D is pretty new, I don't even know if there is an update already...

Other think that occurs to me is that the program you are using to convert the RAW image may not fully support the new format, try using the supplied soft Canon ships w/ the camera to see...

And finally, try to get your hands on another 17-55 to see if the problem persists, if so then the problem is w/ the 7d, if not replace your lens, Canon support seems very efficient in that matter...

Sorry for the bad English...

The firmware is up-to-date and I'm using Canon's Digital Photo Professional. I'll see about checking another lens, though - might not fix that problem, but at least I'll know what the problem is.