Hi Mohsen,
difficult for me to spot the problem, since I don't know what the problem is and you didn't tell us in your e-mail. My Persian is just not good enough to see the fault :)
when I load the Persian .po file into poedit, the string looks the same as in your screenshot, so I assume that poedit and tortoisesvn both display it correctly. Also when I copy the string into this e-mail (see below, don't know if it survives the travel through the internet) it looks "good" to my European eyes.
کمک: برای بارگزاری مجدد زیرشاخه انتخاب شده F5 و برای بارگزاری همه فرزندان Ctrl+F5 را کلیک کنید
There are special characters in Unicode which define the RTL/LTR printing of strings inside strings. Maybe something is already wrong with the translation itself? I can imagine that the order of the substrings is wrong. I would have expected 'Ctrl+F5' to be left of 'F5'.

From: Mohsen Sajjadi [mailto:mohsensajjadi@gmail.com]
Sent: Tuesday, June 10, 2008 1:30 PM
To: dev@tortoisesvn.tigris.org
Subject: problem with rtl view of strings with english characters

hi, i have problem with Persian strings which have English characters inside, as shown in attached image, is there a remedy for this?