How do you stop this?

[greenbuckets]

***** Hand History for Game 1237071351 *****
Hold'em Trny:7524131 Level:4 Stakes (50/100) - Monday, November 29,
05:45:55 EDT 2004
Table Multi-Table(148466) Table #10 (Real Money)
Seat 5 is the button
Total number of players : 10
Seat 2: FerrisState ( $2045 )
Seat 3: Kval14 ( $1993 )
Seat 4: EZED916 ( $420 )
Seat 5: Soapmakers ( $1745 )
Seat 6: alnuts ( $745 )
Seat 7: Qtheskimo ( $1033 )
Seat 8: UdaaMan ( $484 )
Seat 10: dhingy34 ( $1240 )
Seat 9: Club40Deuce ( $705 )
Seat 1: Skyward17 ( $1000 )
Trny:7524131 Level:4
Stakes (50/100)
** Dealing down cards **
Dealt to Soapmakers [ Ks Kc ]
UdaaMan raises [100].
Club40Deuce folds.
dhingy34 raises [150].
Skyward17 folds.
FerrisState folds.
Kval14 folds.
EZED916 folds.
Soapmakers raises [200].
alnuts folds.
Qtheskimo folds.
UdaaMan calls [100].
dhingy34 calls [50].
** Dealing Flop ** [ 6d, 8s, 4c ]
UdaaMan bets [50].
dhingy34 calls [50].
Soapmakers raises [100].
UdaaMan raises [100].
dhingy34 folds.
Soapmakers raises [100].
UdaaMan calls [50].
** Dealing Turn ** [ 2d ]
UdaaMan is all-In.
Soapmakers calls [84].
** Dealing River ** [ As ]
UdaaMan shows [ Ac, 9s ] a pair of aces.
Soapmakers shows [ Ks, Kc ] a pair of kings.
UdaaMan wins 1293 chips from the main pot with a pair of aces.

This happened a few weeks ago but a similar situation occured last night with my Kings being beaten on the river by someone calling my raises with Ace-rag. Keep in mind, this is a limit tourney and the other player was calling raises hoping to catch the ace.

Is it correct to slow down once raises are being called? How long should you continue to bet the overpair? If it was NL, and he went all-in and then hit the ace on the river, that would be one thing, but to continue to call raises with crap is a poor play. With the pre-flop raises, I was putting him on a decent hand such as AQ, AK.