QoS question

I've been getting feedback from callers that they're getting drop-outs and other artifacts of a poor connection when connecting to my FreePBX server.
I'm running 2.6.0.2 on an AMD Athlon XP-based system (with, I think, 512 MB RAM), where my handset (a Linksys SPA941 with 4 lines) is the only active one.
I strongly suspect that it's not the server but the connection back to my provider that is causing the issues, but would welcome any ideas on how I can confirm the source. If it is my provider, I'd be happy to change, but I'd rather be certain before I make the leap.
Thanks,
Des
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Des Dougan



Ping! I'd welcome any
Ping!
I'd welcome any thoughts on why the drop-outs might be occurring.
Thanks,
Des
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Des Dougan