Apologies if this has already been covered but a recent experience(s) prompts me to make this post in the hope that my issues may assist others.
1. Bought a Kingston card on Ebay ....worked fine for a hundred or so shots then started giving error messages when down loading; eventually froze the camera. Replaced card....no more problems. Ebay cards now in trash.
2. At the same time I bought a non Pentax grip, with two extra batteries. Tested this before leaving on this current trip and all worked well. While in the US I bought some Eveready Lithium batteries and put in the grip (assigned the grip as the primary source), into the second full day of shooting the camera froze. Removed grip, took out main battery as well and put it all back and away we went again...all good....for an hour or so
And it froze again.....this time had a close look at the AA lithiums and noticed they were 4X Lithiums, not the 8X I normally buy (memo to buyer: beware; read label!!)...in fact I was not aware there was different Lithiums, which I checked out at the next Walmart, and sure enough, there are !
Anyway, removed battery again, left grip in the bag and all has worked as it should for the last three weeks. I will experiment further when i get home,(preferring to leave well enough alone whilst travelling), but my un-educated guess is that the power drop from 4X lithiums in the grip are the source of my freeze ups.
I think its called living & learning
Hope that helps some one else who may have experienced similar issues.
Cheers