I think I am having the same issue. After completing a call the screen stays black and nothing except restarting it or waiting for several minutes help.
I have fetched the logs from several crashes, here is a tiny bit of one of them:
09-14 12:59:56.965: D/dalvikvm(22801): GC_CONCURRENT freed 564K, 9% free 12611K/13767K, paused 15ms+290ms, total 1163ms
09-14 12:59:56.965: D/FactoryTestApp(22801): [Class] XMLDataStorage , [Method] redefinitionById , [Message] id=LED_GREEN
09-14 12:59:57.115: D/FactoryTestApp(22801): [Class] XMLDataStorage , [Method] redefinitionById , [Message] id=LED_BLUE
09-14 12:59:57.265: D/FactoryTestApp(22801): [Class] XMLDataStorage , [Method] redefinitionById , [Message] id=BAROMETE_DELTA
09-14 12:59:57.265: D/FactoryTestApp(22801): [Class] XMLDataStorage , [Method] redefinitionById , [Message] id=BAROMETE_VENDOR
09-14 12:59:57.790: D/FactoryTestApp(22801): [Class] XMLDataStorage , [Method] redefinitionById , [Message] id=TESTSIM_NOTI
09-14 12:59:58.865: I/FactoryTestApp(22801): [Class] FtClientCPO , [Method] connectToSecPhoneService , [Message] Create sendMessenger - com.sec.phone.SecPhoneService
09-14 13:01:47.900: D/dalvikvm(22731): No JNI_OnLoad found in /system/lib/libcordon.so 0x424d2688, skipping init
09-14 13:05:12.865: D/dalvikvm(9577): GC_CONCURRENT freed 425K, 8% free 12711K/13767K, paused 2ms+102ms, total 1463ms
09-14 13:06:01.475: I/System.out(31369): WMQtt client:Lost connection...
09-14 13:06:05.730: I/com.appcelerator.cloud.push.PushService(31369): MQTT Disonnected
09-14 13:06:31.265: W/com.appcelerator.cloud.push.PushService(31369): MQTT Service status:true
09-14 13:07:16.555: D/SensorManager(2918): Proximity, val = 8.0 [far]
09-14 13:07:20.070: D/InputReader(2259): Input event: value=1
09-14 13:08:21.380: D/SensorManager(2918): Proximity, val = 0.0 [close]
09-14 13:08:21.510: D/SensorManager(2918): Proximity, val = 8.0 [far]
09-14 13:10:45.305: D/dalvikvm(22731): GC_CONCURRENT freed 281K, 7% free 12297K/13191K, paused 8933ms+25245ms, total 151372ms
09-14 13:17:23.150: E/Sensors(2259): poll() failed (Interrupted system call)
09-14 13:17:23.820: I/Process(2259): Sending signal. PID: 2706 SIG: 3
The one in bold is made bold by me since I guess it is significant?
Should I post more of the log?