Occasional fread and cURL slowness

I tried using fread to get an XML document that is generated on the fly from my own Apache web server and it works about 90% of the time and can fetch the document in under a tenth of a second. The other 10% of the time it takes about exactly 5 seconds to fetch the document. I switched to using cURL functions to retrieve the document but I get the same results. 10% of the time it takes almost exactly 5 seconds to fetch the document while most of the time it returns in under a tenth of a second. I have tested and tested loading the same document I am trying to retrieve with fread and cURL in Netscape, IE and with ab (Apache Benchmark) and it never takes 5 seconds to retrieve it so I think something may be wrong with how I am using fread and cURL. Anyone have any thoughts about what may be causing this or how to fix it? Thanks, --Paul