EPG and timeline

[christiand]

TV-Server Version: rc1
MediaPortal Version: rc1
MediaPortal Skin: indigo 1.9
Windows Version: vista sp1
CPU Type: amd athlon x2 4850e
HDD: western digital caviar 1000GP
Memory: 1 GB
Motherboard: Gigabyte 780gam2
Video Card: igp ati 3200
Video Card Driver: ati catalyst 805
Sound Card: onboard realtek
Sound Card AC3:
Sound Card Driver:
1. TV Card: firedtv
1. TV Card Type: terrestial
1. TV Card Driver: final bda drivers
2. TV Card:
2. TV Card Type:
2. TV Card Driver:
3. TV Card:
3. TV Card Type:
3. TV Card Driver:
4. TV Card:
4. TV Card Type:
4. TV Card Driver:
MPEG2 Video Codec: Cyberlink
MPEG2 Audio Codec: MPA
h.264 Video Codec: FFDshow
Satelite/CableTV Provider: Digitenne
HTPC Case: Silverstonetek LC19
Cooling:
Power Supply: built in
Remote: MCE
TV: Benq VL3750
TV - HTPC Connection: DVI->HDMI

I have installed tvserver and connect with a mediaportal client towards it. Everything works allright, but after 6 months of playing with different builds I keep getting a wrong tv epg timeline. On the tv server its set to retrieve the epg from the dvb stream. When I select a program in a mediaportal client the time in the info is correct, but its placed wrong on the timeline. On my latest install there is a difference of about 15 minutes. In my previous build it was about 25 minutes. Is there anyway I can correct this?