We experienced the same problem. Our sistems work on Windows 7 Ultimate x64, and have AVAST PRO installed, we use several portable applications for over six months and all of them work perfectly, then we install the upgrade of AVAST (version 5.1.889, and all portable applications stop working (they do not open, and windows report APPCRASH errors with Event ID: 1000 such as the following ones:
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Faulting application name: Portable Code Visual To Flowchart 5.3.1030.exe, version: 2.1.18.5, time stamp: 0x00000004
Faulting module name: unknown, version: 0.0.0.0, time stamp: 0x00000000
Exception code: 0xc00000fd
Fault offset: 0x00ebb5bf
Faulting process id: 0xcb4
Faulting application start time: 0x01cbbb9fbdeddb04
Faulting application path: C:\Portable Programs\Code_Visual_To_Flowchart_5.3.1030\Portable Code Visual To Flowchart 5.3.1030.exe
Faulting module path: unknown
Report Id: fcae8584-2792-11e0-809c-b8ac6f339358
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Faulting application name: Portable Algebra Equation Solver 7.30.exe, version: 1.0.0.0, time stamp: 0x00000021
Faulting module name: unknown, version: 0.0.0.0, time stamp: 0x00000000
Exception code: 0xc00000fd
Fault offset: 0x00759f7c
Faulting process id: 0xba4
Faulting application start time: 0x01cbbc2b14c1311d
Faulting application path: C:\Portable Programs\Portable_Algebra_Equation_Solver_7.30\Portable Algebra Equation Solver 7.30.exe
Faulting module path: unknown
Report Id: 531de1d2-281e-11e0-a30d-b8ac6f339358
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All our portable applications stop working and produce the same type of erros.... them we unistall AVAST and all applications work perfectly... therefore something is wrong with this new version of AVAST. If AVAST do not produce a fix for this soon we will install another antivirus... this is the seccond time we have problmes with AVAST, last time it delete all our files (over two years of work) when AVAST identify virus on all files on the computer (back in 2010).
Do some one have a solution to this problem with the portable applications?

??