data logger sheild not initializing with UNO

[FinallyME]

A while ago (6 months maybe) I purchased 2 UNOs with 2 data logger shields from Adafruit. I followed the great tutorial and was able to get everything working great. Then, I needed more pins, and switched to a Mega. I was able to get it to work again. Recently, I purchased another data logging shield. With this one, I wanted to put it on the Uno. However, when I loaded the cardinfo sketch, it says :
Initializing SD card...initialization failed. Things to check:
* is a card is inserted?
* Is your wiring correct?
* did you change the chipSelect pin to match your shield or module?

I thought maybe the SD card was bad (I had just formatted it to FAT). But when I tried another card, it did the same thing. So, I put the new logger shield on the Mega, and it worked perfectly. That told me that the SD card works, and the logger shield works. So, I put it on another Uno, and I got the same initialization failed.
At this point, I thought that maybe I messed something up when I switched the files around for the Mega. But, reloading the Arduino files didn't fix the problem. I then took the shield to a friend who had a brand new Uno. He took it out of the packaging to try it out. He also hadn't loaded the new SD file from adafruit. When we tried the logger shield on the new Uno, with a different computer, still the same problem....initialization failed.
The shield still works on the Mega every time I try it, but it won't work on 3 Unos. I also tried other logger shields that work perfectly on Megas, and they do the same on the Unos. I know I am missing something, but don't know what. Any help would be nice.

[adafruit_support_bill]

If you post some clear photos of the front and back of the board we'll see if we can spot any problems.

Also, what version of the UNO were you using? Original? R2? R3?

[FinallyME]

I will get some pictures. All three Unos that I tried are R3s.

[FinallyME]

Here are some pictures:

[adafruit_support_bill]

A few of those solder joints look a little suspect. Some appear not to have flowed well onto the solder pads. Have a look at this guide and retouch anything that looks suspicious. Pay special attention to digital pins 10, 11, 12 & 13, as well as +5, GND, SDA and SCL.

http://learn.adafruit.com/adafruit-guid ... n-problems

[FinallyME]

Holy cow it worked!

I thought for sure that it wouldn't do anything because the shield works perfectly on Megas. That also means I made the exact same soldering error on two other shields that also work on Megas but not Unos. Well, I am glad I posted....and listened to your advice....despite my doubts. Thanks.

[adafruit_support_bill]

Intermittent solder joints are one of the toughest things to debug. But given all the combinations of shields & processors you tried, it sounded like the most likely cause of the problem.