Please send your phone to a Nokia Care Point for inspection if it has the following symptoms when using HSPA (High Speed Packet Access) data connectivity:
- Phone screen turns black but the physical keys under the screen remain lit
- The only way to recover from the condition is to remove the battery
A quick workaround to mitigate the symptom would be to disable High speed packet access via Settings > Connectivity > Admin. settings > Mobile data > High speed packet access > Disabled.Note: With this workaround, you are still using 3G data connectivity, but HSPA is disabled.