I am having similar issues. When I look at the Update Manager logs it is trying to access "http://vibsdepot.hp.com/hpq/feb2013". That is not what I have configured in VUM. This occurs if I point to http://vibsdepot.hp.com/index.xml or http://vibsdepot.hp.com/hpq/oct2012/index.xml.
The /feb2013 folder does not exist on their site, however, some of their packages make reference to it. It looks to be clearly an HP issue, the question is now, how do we get them to fix it.
[2013-02-04 10:33:21:271 'HostUpdateDepotManager' 10644 INFO] [patchDepotManager, 259] Start downloading patch binaries, 3
[2013-02-04 10:33:21:286 'HostUpdateDepotManager' 10644 INFO] [vibDownloaderImpl, 383] Now downloading http://vibsdepot.hp.com/hpq/feb2013/esxi-5x-vibs/hpams/hp-ams-esx-500.9.3.0-13.434156.vib
[2013-02-04 10:33:21:286 'DownloadMgr' 10644 DEBUG] [downloadMgr, 545] Url: http://vibsdepot.hp.com/hpq/feb2013/esxi-5x-vibs/hpams/hp-ams-esx-500.9.3.0-13.434156.vib, Download destination: E:/VMware Update Manager Data/hostupdate/HPQ/feb2013/esxi-5x-vibs/hpams/hp-ams-esx-500.9.3.0-13.434156.vib
[2013-02-04 10:33:21:286 'DownloadMgr' 10644 DEBUG] [downloadMgr, 396] Inserted download job {141585976} to queue
[2013-02-04 10:33:21:286 'DownloadMgr' 10644 DEBUG] [downloadMgr, 416] Current download count: 0
[2013-02-04 10:33:21:286 'DownloadMgr' 10644 DEBUG] [downloadMgr, 432] Current download count: 1
[2013-02-04 10:33:21:286 'DownloadMgr' 10644 DEBUG] [downloadMgr, 438] Adding download job {141585976} to scheduler
[2013-02-04 10:33:21:286 'DownloadMgr' 10644 DEBUG] [downloadMgr, 458] Waiting for download job {141585976} to finish...
[2013-02-04 10:33:21:286 'DownloadMgr' 1972 INFO] [downloadMgr, 593] Executing download job {141585976}, url=http://vibsdepot.hp.com/hpq/feb2013/esxi-5x-vibs/hpams/hp-ams-esx-500.9.3.0-13.434156.vib
[2013-02-04 10:33:21:286 'httpDownload' 1972 INFO] [httpDownload, 571] Downloading http://vibsdepot.hp.com/hpq/feb2013/esxi-5x-vibs/hpams/hp-ams-esx-500.9.3.0-13.434156.vibvia proxy bcproxy1.tsys.com:80
[2013-02-04 10:33:21:442 'httpDownload' 1972 INFO] [httpDownload, 791] Status code: 404
[2013-02-04 10:33:21:442 'httpDownload' 1972 ERROR] [httpDownload, 827] Error retrieving document 'http://vibsdepot.hp.com/hpq/feb2013/esxi-5x-vibs/hpams/hp-ams-esx-500.9.3.0-13.434156.vib'. Status code: 404
[2013-02-04 10:33:21:473 'httpDownload' 1972 INFO] [httpDownload, 926] Retrying http://vibsdepot.hp.com/hpq/feb2013/esxi-5x-vibs/hpams/hp-ams-esx-500.9.3.0-13.434156.vib with proxy off
[2013-02-04 10:33:21:473 'httpDownload' 1972 INFO] [httpDownload, 556] Downloading http://vibsdepot.hp.com/hpq/feb2013/esxi-5x-vibs/hpams/hp-ams-esx-500.9.3.0-13.434156.vib
[2013-02-04 10:33:24:562 'Activation' 11620 INFO] [activationValidator, 367] Leave Validate. Succeeded for integrity.BaselineManager.queryForEntity on target: Integrity.BaselineMgr
[2013-02-04 10:33:24:578 'Activation' 11540 INFO] [activationValidator, 367] Leave Validate. Succeeded for integrity.BaselineGroupManager.queryForEntity on target: Integrity.BaselineGroupManager
[2013-02-04 10:33:33:938 'JobDispatcher' 9748 DEBUG] [JobDispatcher, 405] The number of tasks: 11