I had big crap with mine. I took mine back on saturday to have checked. Got a replacement card on tuesday. Brand new card, sealed in the box. I now have one of those Huawei ones. Much much much much much better. Had one disconnect the whole day today. I spent the whole day connected through the office vpn. The other card went down for hours at a time.
Yip - kudos to Vodacom on this one. Took my busted card in Wed, got a sparkling new Hauwaii 620 this morning. Now I'm back up to speed again... no more bluetooth/GPRS internet for me. (it was a pretty nifty backup though while the 3G was down).