Thanks for your report.
I have sent you an email with a debug version of WinSCP to address you have used to register on this forum.

also, if I try to drag the file out of the window, the program stops working. This is on Win7 SP1 64-bit.
Event viewer entries:
Log Name: Application
Source: Windows Error Reporting
Date: 02/08/2013 15:18:23
Event ID: 1001
Task Category: None
Level: Information
Keywords: Classic
User: N/A
Computer: Chilly
Description:
Fault bucket 3773057557, type 5
Event Name: BEX
Response: Not available
Cab Id: 0

Problem signature:
P1: WinSCP.exe
P2: 5.1.6.3394
P3: 00000000
P4: StackHash_4c4a
P5: 0.0.0.0
P6: 00000000
P7: 00000001
P8: c0000005
P9: 00000008
P10:

Attached files:
C:\Users\Shaun\AppData\Local\Temp\WER31D5.tmp.WERInternalMetadata.xml

These files may be available here:
C:\Users\Shaun\AppData\Local\Microsoft\Windows\WER\ReportArchive\AppCrash_WinSCP.exe_8b60caacf5d54cbffbf9d9d9e6f562ff5d93801c_11e4bdfe

Analysis symbol:
Rechecking for solution: 0
Report Id: 4ddace75-fb7e-11e2-87b9-00268311740c
Report Status: 0
Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
<System>
<Provider Name="Windows Error Reporting" />
<EventID Qualifiers="0">1001</EventID>
<Level>4</Level>
<Task>0</Task>
<Keywords>0x80000000000000</Keywords>
<TimeCreated SystemTime="2013-08-02T14:18:23.000000000Z" />
<EventRecordID>18906315</EventRecordID>
<Channel>Application</Channel>
<Computer>Chilly</Computer>
<Security />
</System>
<EventData>
<Data>3773057557</Data>
<Data>5</Data>
<Data>BEX</Data>
<Data>Not available</Data>
<Data>0</Data>
<Data>WinSCP.exe</Data>
<Data>5.1.6.3394</Data>
<Data>00000000</Data>
<Data>StackHash_4c4a</Data>
<Data>0.0.0.0</Data>
<Data>00000000</Data>
<Data>00000001</Data>
<Data>c0000005</Data>
<Data>00000008</Data>
<Data>
</Data>
<Data>
C:\Users\Shaun\AppData\Local\Temp\WER31D5.tmp.WERInternalMetadata.xml</Data>
<Data>C:\Users\Shaun\AppData\Local\Microsoft\Windows\WER\ReportArchive\AppCrash_WinSCP.exe_8b60caacf5d54cbffbf9d9d9e6f562ff5d93801c_11e4bdfe</Data>
<Data>
</Data>
<Data>0</Data>
<Data>4ddace75-fb7e-11e2-87b9-00268311740c</Data>
<Data>0</Data>
</EventData>
</Event>
--------------------------------------
Log Name: Application
Source: Application Error
Date: 02/08/2013 15:17:47
Event ID: 1000
Task Category: (100)
Level: Error
Keywords: Classic
User: N/A
Computer: Chilly
Description:
Faulting application name: WinSCP.exe, version: 5.1.6.3394, time stamp: 0x00000000
Faulting module name: unknown, version: 0.0.0.0, time stamp: 0x00000000
Exception code: 0xc0000005
Fault offset: 0x00000001
Faulting process id: 0x3fec
Faulting application start time: 0x01ce8f8b0669c12f
Faulting application path: C:\Program Files (x86)\WinSCP\WinSCP.exe
Faulting module path: unknown
Report Id: 4ddace75-fb7e-11e2-87b9-00268311740c
Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
<System>
<Provider Name="Application Error" />
<EventID Qualifiers="0">1000</EventID>
<Level>2</Level>
<Task>100</Task>
<Keywords>0x80000000000000</Keywords>
<TimeCreated SystemTime="2013-08-02T14:17:47.000000000Z" />
<EventRecordID>18906314</EventRecordID>
<Channel>Application</Channel>
<Computer>Chilly</Computer>
<Security />
</System>
<EventData>
<Data>WinSCP.exe</Data>
<Data>5.1.6.3394</Data>
<Data>00000000</Data>
<Data>unknown</Data>
<Data>0.0.0.0</Data>
<Data>00000000</Data>
<Data>c0000005</Data>
<Data>00000001</Data>
<Data>3fec</Data>
<Data>01ce8f8b0669c12f</Data>
<Data>C:\Program Files (x86)\WinSCP\WinSCP.exe</Data>
<Data>unknown</Data>
<Data>4ddace75-fb7e-11e2-87b9-00268311740c</Data>
</EventData>
</Event>

Just upgraded to this version: now when I try to edit a file by double-clicking, I get the invalid access to memory error. If I right-click and choose edit, I get Access violation at address 00000000. Write of address 00000000