The two most frequent issues that generally come up, are that the BES Client is running the installation using the LocalSystem account, and the BES client is running in 32-bit mode.
The easiest way to test these is by using psexec from www.microsoft.com/sysinternals.
You’d use
psexec -i -s c:\windows\system32\cmd.exe to open a 64-bit command prompt and use that to see if your setup works ok using the LocalSystem account.
Next, try using
psexec -i -s c:\windows\syswow64\cmd.exe to see if it still works using the LocalSystem account in 32-bit mode.
Let us know whether either or both of these fail and we can help with workarounds for each.