For the past few days we have been unable to qualify leads.
One can open a lead, click qualify, the pop-up appears, select Account + Opportunity, confirm, the Duplicate Detection window pops up and then regardless of whether duplicates exist or not, clicking Save Record will cause Dynamics to hang.
On some machines the Duplicate Detection window simply disappears and the lead window remains all greyed out without anything happening (refreshing the window shows that the lead is still active and the Account+Opportunity did not get created).
On other machines, a Script Error window is displayed pointing towards lead.js (error message: 
)
I've identified that the Duplicate Detection rules are somehow related - this error only happens if fields which are checked are filled (Name, Phone Number and Email). Disabling the duplicate detection fixes the qualifying however Duplicate Detection is critical to our use of the CRM.
Any ideas/tips/pointers on what might be causing this?
Best,
Ollie