Audio dissolves sound crackly

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I've been noticing my audio dissolves sound crackly. All audio sounds fine, except for certain areas where I've either dissolved between two audio clips or dissolved an audio clip to nothing. Music seems to be worse (as opposed to dialogue).
Any ideas? Could it have something to do with my hardware?
I'm using Premiere Pro 1.5

WinXP Pro SP2
Soundblaster X-Fi
P4 2.4GHz
2Gb DDR400

Thanks in advance!