When testing "on several differnet internet connections", do you mean as a client browsing the store, OR do you mean you've tried zencart itself on a 'different internet connection"?
If the former, you aren't really proving anything. The quotes rely on the connectivity of the zencart server to the quotation servers. Where the 'client' is connecting from is of no relevance.
As I said, the servers haven't been down for a LONG time (months), so your problem is almost certain to be on your server hosts side of things. Many 'shared' hosts are grossly overloaded and intermittent timeouts are not uncommon.
Cheers
Rod
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