mongoexport produced this:
{ "_id" :

{ "millis" : 1288603364761, "ptn" : "-12979677046105402" }

, "sessionId" : "e327d914-3924-4bb3-8ad0-99a35bc997d8", }

which mongoimport puked on:

Fri Mar 11 10:03:35 Assertion: 10340:Failure parsing JSON string near: , }
0x100091b1b 0x100031b1e 0x100446ae7 0x100448675 0x100440e9d 0x10044647e 0x100001a04 0x6
0 mongoimport 0x0000000100091b1b _ZN5mongo11msgassertedEiPKc + 315
1 mongoimport 0x0000000100031b1e _ZN5mongo8fromjsonEPKcPi + 1406
2 mongoimport 0x0000000100446ae7 _ZN6Import9parseLineEPc + 167
3 mongoimport 0x0000000100448675 _ZN6Import3runEv + 3733
4 mongoimport 0x0000000100440e9d _ZN5mongo4Tool4mainEiPPc + 2989
5 mongoimport 0x000000010044647e main + 62
6 mongoimport 0x0000000100001a04 start + 52
7 ??? 0x0000000000000006 0x0 + 6
exception:Failure parsing JSON string near: , }
{ "_id" :

{ "millis" : 1288603364761, "ptn" : "-12979677046105402" }

, "sessionId" : "e327d914-3924-4bb3-8ad0-99a35bc997d8", }