Why is the App Store unable to download the Xcode update?

Question

After installing Yosemite, I went to the App Store to update several apps. Most were updated without any difficulty. However, when it got to the Xcode update for v6.1, I get the message, "An error occurred during purchase." with buttons to Cancel or Retry. Multiple tries produce the same result. The information block states the price is "Free" as it always has been. Something needs repair.
Thank you,
Doug

Answer 1

Modified approach: Went to System Log Queries and looked at All messages. Inserted Marker, then tried again with these lines produced in All Messages:
10/26/14 11:39:50.444 PM Console[4758]:  Marker - Oct 26, 2014, 11:39:50 PM
10/26/14 11:39:57.016 PM storeaccountd[555]: AccountServiceDelegate: Accepting new connection <NSXPCConnection: 0x7f87d7a7e040> connection from pid 2408 with interface <AccountServiceInterface: 0x7f87d7a7b2c0> (PID 2408)
10/26/14 11:39:57.062 PM storeaccountd[555]: ADI: {
    "Cache-Control" = "no-transform, max-age=14400";
    Connection = "keep-alive";
    "Content-Encoding" = gzip;
    "Content-Length" = 21059;
    "Content-Type" = "text/xml; charset=UTF-8";
    Date = "Mon, 27 Oct 2014 03:39:57 GMT";
    "Last-Modified" = "Mon, 27 Oct 2014 02:30:57 GMT";
    Server = "ATS/4.1.0";
    Vary = "Accept-Encoding, X-Apple-Store-Front, Cookie, User-Agent";
    "X-Apple-ATS-Cache-Key" = "/init.itunes.apple.com/80/WebObjects/MZInit.woa/wa/initiateSession/MacAppStore /2.0%20/143441-1/13/https/itspod=16?ix=5";
    "X-Apple-Partner" = "origin.0";
    "apple-timing-app" = "44 ms";
    "x-apple-aka-ttl" = "Generated Sun Oct 26 19:30:57 PDT 2014, Expires Mon Oct 27 01:10:57 PDT 2014, TTL 20400s";
    "x-apple-application-instance" = 31024;
    "x-apple-application-site" = ST11;
    "x-apple-jingle-correlation-key" = XWJHEECH2TPW4;
    "x-apple-max-age" = 14400;
    "x-apple-orig-url" = "https://init.itunes.apple.com/WebObjects/MZInit.woa/wa/initiateSession?ix=5&user AgentCacheKey=MacAppStore%2f2.0%20";
    "x-apple-request-store-front" = "143441-1,13";
    "x-apple-translated-wo-url" = "/WebObjects/MZInit.woa/wa/initiateSession?ix=5&userAgentCacheKey=MacAppStore%2 f2.0%20";
    "x-webobjects-loadaverage" = 0;
10/26/14 11:39:57.099 PM storeaccountd[555]: AccountServiceDelegate: Accepting new connection <NSXPCConnection: 0x7f87d7b13ac0> connection from pid 2408 with interface <AccountServiceInterface: 0x7f87d7b20d50> (PID 2408)
10/26/14 11:39:57.108 PM storeaccountd[555]: AccountServiceDelegate: Accepting new connection <NSXPCConnection: 0x7f87d5f171c0> connection from pid 2408 with interface <AccountServiceInterface: 0x7f87d5f94550> (PID 2408)
10/26/14 11:39:57.113 PM storeaccountd[555]: AccountServiceDelegate: Accepting new connection <NSXPCConnection: 0x7f87d7b30ee0> connection from pid 2408 with interface <AccountServiceInterface: 0x7f87d7b31210> (PID 2408)
10/26/14 11:39:57.223 PM storeuid[2350]: UIServiceDelegate: Accepting new connection <NSXPCConnection: 0x7ff2f251a120> connection from pid 2408 with interface <UIServiceInterface: 0x7ff2f2503850> (PID 2408)
10/26/14 11:39:57.225 PM storeaccountd[555]: ADI: {
    "Cache-Control" = "private, no-cache, no-store, no-transform, must-revalidate, max-age=0";
    Connection = "keep-alive";
    "Content-Encoding" = gzip;
    "Content-Length" = 118;
    "Content-Type" = "text/xml; charset=UTF-8";
    Date = "Mon, 27 Oct 2014 03:39:57 GMT";
    Expires = "Mon, 27 Oct 2014 03:39:57 GMT";
    "Set-Cookie" = "Pod=16; version=\"1\"; expires=Thu, 27-Nov-2014 04:39:57 GMT; path=/; domain=.apple.com, itspod=16; version=\"1\"; expires=Thu, 27-Nov-2014 04:39:57 GMT; path=/; domain=.apple.com";
    "apple-timing-app" = "10 ms";
    "edge-control" = "no-store, cache-maxage=0";
    itspod = 16;
    pod = 16;
    "x-apple-application-instance" = 162192;
    "x-apple-application-site" = NWK;
    "x-apple-jingle-correlation-key" = OWDNCY77DVDWS;
    "x-apple-lokamai-no-cache" = true;
    "x-apple-orig-url" = "https://p16-buy.itunes.apple.com/WebObjects/MZBuy.woa/wa/buyProduct?guid=0023323 18C8C";
    "x-apple-translated-wo-url" = "/WebObjects/MZBuy.woa/wa/buyProduct?guid=002332318C8C";
    "x-frame-options" = SAMEORIGIN;
    "x-webobjects-loadaverage" = 0;
10/26/14 11:39:57.233 PM storeaccountd[555]: AccountServiceDelegate: Accepting new connection <NSXPCConnection: 0x7f87d5ddfa90> connection from pid 4783 with interface <AccountServiceInterface: 0x7f87d5d85080> (PID 4783)
10/26/14 11:40:09.167 PM storedownloadd[587]: DownloadServiceDelegate: Accepting new connection <NSXPCConnection: 0x7feda7f079b0> connection from pid 2408 with interface <DownloadServiceInterface: 0x7feda7f11dd0> (PID 2408)
Does this provide any information?