Help, 99% of files play choppy. Can anyone help

Hello. I have installed Win7 mkv and I can play mkv files perfectly without sound. Once I install AC3filter, or any other audio codec 99% of the files become super choppy and unplayable. Can anyone help. I have included the mediainfo of these two files.

The one that works:
General
Format : Matroska
File size : 2.18 GiB
Duration : 50mn 51s
Overall bit rate : 6 140 Kbps
Movie name : Planet.Earth.EP04.Caves.2006.720p.HDDVD.x264-ESiR
Encoded date : UTC 2007-05-11 19:11:44
Writing application : mkvmerge v2.0.2 ('You're My Flame') built on Feb 21 2007 23:40:55
Writing library : libebml v0.7.7 + libmatroska v0.8.1
Cover : Yes / Yes

Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile :
Format settings, CABAC : Yes
Format settings, ReFrames : 9 frames
Muxing mode : Container profile=Unknown@5.1
Codec ID : V_MPEG4/ISO/AVC
Duration : 50mn 47s
Bit rate : 5 567 Kbps
Nominal bit rate : 5 690 Kbps
Width : 1 280 pixels
Height : 720 pixels
Display aspect ratio : 16/9
Frame rate : 23.976 fps
Resolution : 24 bits
Colorimetry : 4:2:0
Scan type : Progressive
Bits/(Pixel*Frame) : 0.252
Stream size : 1.98 GiB (91%)
Title : Planet Earth - EP04 - Caves
Writing library : x264 core 54 svn-635M
Encoding settings : cabac=1 / ref=6 / deblock=1:-1:-1 / analyse=0x3:0x133 / me=umh / subme=7 / brdo=1 / mixed_ref=1 / me_range=24 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=2 / deadzone=21,11 / chroma_qp_offset=0 / threads=2 / nr=0 / decimate=0 / mbaff=0 / bframes=4 / b_pyramid=1 / b_adapt=1 / b_bias=0 / direct=1 / wpredb=1 / bime=1 / keyint=250 / keyint_min=25 / scenecut=40(pre) / rc=2pass / bitrate=5690 / ratetol=1.0 / rceq='blurCplx^(1-qComp)' / qcomp=0.60 / qpmin=10 / qpmax=51 / qpstep=4 / cplxblur=20.0 / qblur=0.5 / ip_ratio=1.40 / pb_ratio=1.30 / aq=1:0.5:18.0
Language : English

Audio
ID : 2
Format : AC-3
Format/Info : Audio Coding 3
Codec ID : A_AC3
Duration : 50mn 51s
Bit rate mode : Constant
Bit rate : 448 Kbps
Channel(s) : 6 channels
Channel positions : Front: L C R, Surround: L R, LFE
Sampling rate : 48.0 KHz
Stream size : 163 MiB (7%)
Title : AC3 5.1
Language : English

Text #1
ID : 3
Format : ASS
Codec ID : S_TEXT/ASS
Codec ID/Info : Advanced Sub Station Alpha
Language : English

Text #2
ID : 4
Format : ASS
Codec ID : S_TEXT/ASS
Codec ID/Info : Advanced Sub Station Alpha
Language : Romanian

The One that DOesn't
General
Complete name : Format : Matroska
File size : 3.58 GiB
Duration : 1h 44mn
Overall bit rate : 4 918 Kbps
Encoded date : UTC 2009-06-18 21:52:48
Writing application : mkvmerge v2.9.5 ('Tu es le seul') built on Jun 7 2009 11:07:07
Writing library : libebml v0.7.7 + libmatroska v0.8.1

Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile :
Format settings, CABAC : Yes
Format settings, ReFrames : 5 frames
Muxing mode : Container profile=Unknown@4.1
Codec ID : V_MPEG4/ISO/AVC
Duration : 1h 44mn
Bit rate : 4 371 Kbps
Nominal bit rate : 4 468 Kbps
Width : 1 280 pixels
Height : 528 pixels
Display aspect ratio : 2.424
Frame rate : 23.976 fps
Resolution : 24 bits
Colorimetry : 4:2:0
Scan type : Progressive
Bits/(Pixel*Frame) : 0.270
Stream size : 3.18 GiB (89%)
Writing library : x264 core 67 r1160 ea224ee
Encoding settings : cabac=1 / ref=5 / deblock=1:0:0 / analyse=0x3:0x133 / me=umh / subme=7 / psy_rd=1.0:0.0 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=0 / deadzone=21,11 / chroma_qp_offset=-2 / threads=12 / nr=0 / decimate=1 / mbaff=0 / bframes=3 / b_pyramid=1 / b_adapt=1 / b_bias=0 / direct=1 / wpredb=1 / keyint=250 / keyint_min=25 / scenecut=40 / rc=2pass / bitrate=4468 / ratetol=1.0 / qcomp=0.60 / qpmin=10 / qpmax=51 / qpstep=4 / cplxblur=20.0 / qblur=0.5 / ip_ratio=1.40 / pb_ratio=1.30 / aq=1:1.00
Language : English

Audio
ID : 2
Format : AC-3
Format/Info : Audio Coding 3
Codec ID : A_AC3
Duration : 1h 44mn
Bit rate mode : Constant
Bit rate : 448 Kbps
Channel(s) : 6 channels
Channel positions : Front: L C R, Surround: L R, LFE
Sampling rate : 48.0 KHz
Stream size : 334 MiB (9%)
Language : English

Text
ID : 3
Format : UTF-8
Codec ID : S_TEXT/UTF8
Codec ID/Info : UTF-8 Plain Text
Language : English

I am running Win7 RC, INtel core2 duo 2.4ghz with 4 gigs of ram and Nvidia 8800 Ultra.

Please help.