We just migrated from 2007 to 2010 and changed our stylesheets to use v4. We have a list of over 1000 items with a few "Link URL" columns. Occasionally when editing the item, the link url field would not show the "Click to add a new hyperlink" in order to add a link. This "Click to add.." shows for other hyperlink fields in the same record, but not for this particular field. For the same field, it shows in other records. So very sporadic. Sometimes the link value vanishes and there is no way I can add it back unless I delete and readd, which is painful as it seems to happen frequently. Anyone seen such an issue?
I did double check that publishing hyperlink has issues updating the values and the link vanishes, without a chance to add a new link. Very likely a SharePoint bug. However I wrote a small script that would update the link via powershell. I have updated the solution in my blog vasya10.wordpress.com.