Just my two cents:
I think a lot of the time people that play higher levels go down a few levels and don't realise that the people they're playing against simply don't think about the cards the same way they do. At 2nl, people aren't really thinking: Okay, what's my equity, what does my opponent think I have, what does my opponent think I think they have etc. The good players at 2nl are generally just playing their cards, the bad players are just spewing all over the place; which is probably why you're seeing a lot of wtf bad play when you moved back down to 2nl.
Also, for the record, 2nl is most definitely NOT harder to play than high stakes play money.
I go look at highest stakes play money table and this is first hand. Find me a 2NL table where you seem someone in a 560bb pot and turns over a gutshot
pokerstars Hand #77649208528: Hold'em No Limit (100/200) - 2012/03/22 23:50:39 WET [2012/03/22 19:50:39 ET]
Table 'Aase II' 9-max (Play Money) Seat #6 is the button
Seat 1: vlademir vla (34100 in chips)
Seat 2: zorro237 (39300 in chips)
Seat 3: boss630713 (120400 in chips)
Seat 4: brasuca1963 (548900 in chips)
Seat 5: emilio1932 (9100 in chips)
Seat 6: marcmarq (99200 in chips)
Seat 7: 38bandit (334600 in chips)
Seat 8: CARBI_RJ (43500 in chips)
Seat 9: zamfir_alin (339225 in chips)
38bandit: posts small blind 100
CARBI_RJ: posts big blind 200
*** HOLE CARDS ***
zamfir_alin: calls 200
vlademir vla: calls 200
zorro237: folds
boss630713: calls 200
brasuca1963: calls 200
emilio1932: raises 8900 to 9100 and is all-in
marcmarq: folds
38bandit: folds
CARBI_RJ: folds
zamfir_alin: calls 8900
vlademir vla: calls 8900
boss630713: folds
brasuca1963: calls 8900
*** FLOP *** [Jd 2s 5s]
zamfir_alin: checks
vlademir vla: checks
brasuca1963: bets 15200
zamfir_alin: calls 15200
vlademir vla: calls 15200
*** TURN *** [Jd 2s 5s] [Jh]
zamfir_alin: checks
vlademir vla: checks
brasuca1963: bets 9800
zamfir_alin: calls 9800
vlademir vla: calls 9800 and is all-in
*** RIVER *** [Jd 2s 5s Jh] [Tc]
zamfir_alin: checks
brasuca1963: checks
*** SHOW DOWN ***
zamfir_alin: shows [Ah 3c] (a pair of Jacks)
vlademir vla: shows [Td Ts] (a full house, Tens full of Jacks)
brasuca1963: mucks hand
vlademir vla collected 75000 from side pot
emilio1932: mucks hand
vlademir vla collected 36900 from main pot
*** SUMMARY ***
Total pot 111900 Main pot 36900. Side pot 75000. | Rake 0
Board [Jd 2s 5s Jh Tc]
Seat 1: vlademir vla showed [Td Ts] and won (111900) with a full house, Tens full of Jacks
Seat 2: zorro237 folded before Flop (didn't bet)
Seat 3: boss630713 folded before Flop
Seat 4: brasuca1963 mucked
Seat 5: emilio1932 mucked
Seat 6: marcmarq (button) folded before Flop (didn't bet)
Seat 7: 38bandit (small blind) folded before Flop
Seat 8: CARBI_RJ (big blind) folded before Flop
Seat 9: zamfir_alin showed [Ah 3c] and lost with a pair of Jacks