I've recently rolled my own as far as I2C connectors go. The connector itself is not very important, right now I'm just using 100mil pitch header (usually female on board so it's not so pokey when not connected), but any 4plus pin connector will do. Additionally, I'm using the P82B715 from TI as an I2C bus extender. This overcomes the capacitance issues associated with running long I2C drops off board, which as people have been saying, I2C was not intended for initially. I did try many different combinations, like in the examples you gave and I noticed absolutely no difference in performance. I believe this is because I2C is relatively slow, interference between SDA and SCL is not much of an issue. Basically the rise time for voltages (when interference will occur) on the bus are much much smaller than a bit length. So, that may not be what you want to hear, but it does afford more options. Personally I went with [VCC, SDA, GND, SCL] to be easily routed to/from this chip and also be immune to a VCC/GND mix up when plugged in backward.
Since your I2C works at 100Khz, but not 400 Khz, it is a good idea to look at the various factors that have an effect on timing.
1: Check that your slave board supports 400Khz.
2: Resistor values are too big.
When the timing is increased from 100k to 400k, the period of the clock drops from 10 us to 2.5 us.
This means that the rising edge of your data/clock signals has a significantly less amount of time to settle. the time taken is calculated as follows:
t = rc
the capacitance on the bus is usually constant and a property of each device. It sounds like you have these. Add them up.
The resistor values are the next variable. Since you have three in parallel, you need to add them using 1/Rt = 1/R1 + 1/R2 + 1/R3 and so on. You only need one resistor on the bus, so having three in parallel is going to lower the total resistance.
You can now calculate t using the above formula. If it is more than 300ns (just over 10% of your clock period at 400k), then the rise time is out of I2C spec. Here, table 5, page 32.
If you'd like to calculate the correct resistor value, you can re-arrange the above formula to get R=t/c and work from there, where T is 300ns or less.
Best Answer
Should be fine,if the voltage on the pullup is at an acceptable on for the slave and the master. If not, you need a level shifter. Also, you need to pay attention to total cable capacitance if you want to keep your speed up. You might need to use smaller resistors than you expect.
http://www.edn.com/design/analog/4371297/Design-calculations-for-robust-I2C-communications seems like a good reference.