getting error "The server block is not well formed" in netframework.aspx
<p>I opened up a large asp.net project in Visual Studio 2010; the project hadn't been touched for a couple of months, and the last time I had it opened, it built fine. But today it's getting errors during the build -- EDIT -- actually, Build and Rebuild both work; it's not until I try to Start Debugging that the errors occur.</p>

<pre><code>  DESCRIPTION.............................FILE...............LINE
 "The server block is not well formed"    netframework.aspx  275150
</code></pre>

<p>and the following unreadable garbage:</p>

<blockquote>
  <p>Literal expressions like '&lt;%$ AëÜË    ¾ø2µ¬GP‰¦M†M²·tÕEôâ3)úè¦¢Š7*ÃGzü‰v;§h¿ñÒÿÕùhXY&amp;˜ŠÐ÷Îç&amp;þÊoaãÙ,–ûm…iû^|J[jÜÏ±­R[˜ó-ü×?¦S8I FÙ<code>œ</code>h¶©)CO-qz†ô—„<em>„mó+‚ìW¼„ý–åC6Emo«„>v¥>¨C,íc«2•dŸwì9+®Vù@üãwš^(œè Î¾ñF4×ME½Ú"ÝÚd$eO›N ‹˜Î8±°K×E&lt;·NØKäµ)›‚Ù¥¬ ý—Ÿ##”e¸fšæPÐ{³ãQèëZ/G</em>½Ci„å…€bØÇ½á_$ÄøÛ±ÝÆÅÇÀáèÅš¼”kôX¨ÇHŽEŸñÎ˜LJÑ”NÀ$_ü€ô>$Y,I ¥u»dFÒ~WH*”D:ì1&lt;:êª©[k¥õ²éÍ"ìâ®hàŽ)Ûp7”d—rTÚÇICýp†5Å«¡@ØJª‡è›Þ"RËŠÚ‰Åi‰ï/ªîë 7±¶cYJ¯¬—àÖ’öGUéÒ ;î’mõnÛ¿Xè‹Oñ&amp;BÉ¸Ä}ŽåíXÑ­¬¯ë3Ê*’;ëÔÙÆv½‡ sk)¾ÀÈBk±mvõò3c]¾UsLq/¶Ùî~')ÛraÀÖ,ó››Kì¦é…¾QtÃ$šÁl¸"èGæ¨˜´aÔ}qÛžòn!=ÎéCáê©H¢J7C5ˆQ»™bXO“ø³ê¶®^'d0ï0”ÃæBD›“©/©;“îqe_Åk/k“‚ Îµ­hnŸëœÍ&lt;07Ó@ñ""'ÐÒ—g UQ5ósžýªí”vÓZ"\yzÈ„+ø_V»;wlmùÎ ñI+è¬“ª‚­ ãpñ+ÜŸt”z­SŠÈPíÒÑðw9#DUpÞJ«vú  C:\inetpub\wwwroot\MYAPP\netframework.aspx  177272  </p>
</blockquote>

<p>How do I begin to troubleshoot these errors in a large project?  As I said, last time it was opened it built fine--- EDIT: and ran fine.  </p>
