IIS 7 Application Pool crashing

I have 8 web sites hosted in IIS 7 on Windows Server 2008 R2 64bit SP1. Hardware, in case it matters, is a Dell M610 blade, dual Xeon X5675 3GHz 24GB RAM (generally only using half of that at peak times). Each web site has it's own app pool and they all run smoothly except one app pool, which keeps crashing, resulting in 503 errors. The logs are full of events such as below. How can I pinpoint the issue and resolve this promptly as it affects thousands of users and keels over daily?

EVENT ID: 1001
Fault bucket , type 0
Event Name: BEX
Response: Not available
Cab Id: 0

Problem signature:
P1: w3wp.exe
P2: 7.5.7601.17514
P3: 4ce7a5f8
P4: MSVCR90.dll
P5: 9.0.30729.6161
P6: 4dace5b9
P7: 0006ccd5
P8: c0000417
P9: 00000000
P10:

Attached files:

These files may be available here:
C:\ProgramData\Microsoft\Windows\WER\ReportQueue\AppCrash_w3wp.exe_33c4ab5dd626322a48afa7bd257a8826b51ed21e_71f49cea

Analysis symbol:
Rechecking for solution: 0
Report Id: 22f3c673-5148-11e2-9212-24b6fd689de1
Report Status: 0
*******************************************

EVENT ID: 1000
Faulting application name: w3wp.exe, version: 7.5.7601.17514, time stamp: 0x4ce7a5f8
Faulting module name: MSVCR90.dll, version: 9.0.30729.6161, time stamp: 0x4dace5b9
Exception code: 0xc0000417
Fault offset: 0x0006ccd5
Faulting process id: 0x2d48
Faulting application start time: 0x01cde554d94169b3
Faulting application path: C:\Windows\SysWOW64\inetsrv\w3wp.exe
Faulting module path: C:\Windows\WinSxS\x86_microsoft.vc90.crt_1fc8b3b9a1e18e3b_9.0.30729.6161_none_50934f2ebcb7eb57\MSVCR90.dll
Report Id: 22f3c673-5148-11e2-9212-24b6fd689de1