Unable to open a decompression stream. Code = 8

[Magictest]

I can hear event sounds/play clicks, others can hear me, but I cannot hear other people talking. When I go into testing I get the error "Unable to open a decompression stream. Code = 8" for the GSM 6.10 Codec, but the Speex codec works fine.

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I found a possible solution:[FONT=Verdana](Windows XP)[/FONT]
[FONT=Verdana]Control Panel > Sounds and Audio > Hardware Tab[/FONT]
[FONT=Verdana]Double click "Audio Codecs" > Properties Tab[/FONT]
[FONT=Verdana]Double click on msgsm32.acm[/FONT]
[FONT=Verdana]Click settings[/FONT]
[FONT=Verdana]Set Compress and Decompress to “All rates” [/FONT]
[FONT=Verdana]Press OK (4 times)[/FONT]
HOWEVER its for Windows XP.
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I'm using windows 7, and I can't find a way to edit my codecs.
I have tried various solutions already:
-reinstalling GSM 6.10 codec through deleting/reinstalling windows media player but it did not reinstall the codec.
-c-panel / sounds / playback / select device / properties / advanced tab / select one of the 44khz settings. Still same decompression error.
-Reinstalled new version of Ventrillo.
-Copy/pasted a msgsm32.acm file from another computer where it works. Still same error.

Any help would be very appreciated