Biztalk AS2 encryption error for file bigger than 100MB

Question

I am getting following error when I am trying to receive file bigger than 100 MB. I was getting same error when I was trying file bigger than 5MB and I applied windows CU5. Now I can receive big file (I tested till 60 MB). New file which is coming is 110MB
and we start getting this error. 
Can somebody help me to figure out this issue.
I am using Biztalk 2010 with windows 2008 server
A message received by adapter "HTTP" on receive location "RecLocAS2All" with URI "/xxxxxx/BTSHTTPReceive.dll" is suspended. 
 Error details: An output message of the component "Microsoft.BizTalk.EdiInt.PipelineComponents" in receive pipeline "Microsoft.BizTalk.EdiInt.DefaultPipelines.AS2Receive, Microsoft.BizTalk.Edi.EdiIntPipelines, Version=3.0.1.0, Culture=neutral,
PublicKeyToken=31bf3856ad364e35" is suspended due to the following error: 
     An error occurred when decrypting an AS2 message..
 The sequence number of the suspended message is 2.  

Answer 1

I tried passthrough pipeline and I can receive encrypted file.Now trying to write code to decrypt it but I can not. Based on certificate I can say it is RSASHAI, so using it for decrypt. But getting error at  Convert.FromBase64String(text) where text
is encrypted test from file.
I am getting following error 
The input is not a valid Base-64 string as it contains a non-base 64 character,
more than two padding characters, or an illegal character among the padding characters.
Can somebody help me to understand it and resolve this. Mean time trying
to convene customer for compressed file .Please help me to understand above error.