I'll say it again - Combom has one of the most interesting blogs around dealing with 'Doctor Who' (although that's not the sole focus of his site.)
And with the episode of 'The Sarah Jane Adventures' which gave Sarah Jane - and Jo Grant! - the chance to meet the Eleventh Incarnation of the Doctor ("Death Of The Doctor"), he found a serious flaw in the plot-line:
So the whole plan of the Sarah Jane Adventures Death Of The Doctor was to have Sarah Jane Smith and Jo Grant to think about the TARDIS key, and make one from their memories using the Memory Weave. OK I fall for that, however...
The TARDIS key started off as Yale style, like it is today, however at some point during the third Doctor, he began experimenting with new designs for the TARDIS key, coming up with several alternative designs, settling on a spade-shaped silver key. The Fourth Doctor experimented with even more radical designs, which included a double-helix apparently made of plastic, before eventually going back to the Yale style for the ninth Generation.
So Jo Grants memory of the TARDIS key may not be of the Yale type it is today, and unless Sarah Jane has had a good look at the key recently (unlikely), she will remember a non-Yale style. I think it would have made for a far more interesting story - if not exactly as action-packed as the TV gods probably demanded - for the key that was finally created out of the Memory Weave turned out to be that strange key pictured above. I don't know how the story would have proceeded from that point - and we would have probably lost the opportunity to see all those memories from the old series dredged up from the minds of Sarah Jane and Jo - but sci-fi doesn't always have to be about overloaded circuits and their resultant explosions.
And if you really needed all of that flash, it still could have happened. Sarah Jane and Jo could have remembered different versions of the TARDIS key, which the Memory Weave probably couldn't reconcile. That would still lead to the circuits overloading and a big boom, bye-bye baddies.