jerking and dash lights flashing when stopped or at low speed...HELP!!

[justn_m]

2003 1.8T jetta wagon........It has a new Bosch alternator (6 months old) and a new battery (1 month old - warranty replacement)

The other day my wife was stopped in line at the bank when she said that the car jumped forward like someone hit her in the rear and all the dash lights started flashing....started driving and it went away. 3 days later....she drove about 40 miles and was sitting still in traffic and it happened again. She unplugged GPS, Ipod, etc... and cut off A/C and it stopped and she made it to her destination. She drove home fa ew hours later and it was fine.
I did read about the ground wire on the tranny being corroded could be an issue with charging...i thought i would check that..
I had the alternator tested when the new battery was installed and it is charging....per the test (think it was 13.3V)
I am not sure what to check....could it be another bad battery (AutoZONE)?

Help
-Justin