In my case there was no section for the Alert.aspx in the web.config file (I was having the problem on the Alerts link) so I had to add the following section/lines to the web.config file and it fixed the problem on the Alerts link. Note that I had tried the Database Manager solution provided by byrona but there was no entry for my userid nor was there a default entry to modify so I did not know what to change so I opted to modify the web.config file instead):
Added the following lines to the inetpub\SolarWinds\web.config file to solve this problem with Alerts link:
<location path="Orion/NetPerfMon/Alerts.aspx">
<system.web>
<httpRuntime maxRequestLength="1048576" executionTimeout="300" />
</system.web>
</location>
My version are as follows for your reference:
Orion Platform 2014.2.1, SAM 6.1.1, QoE 1.0, NCM 7.3.1, NPM 11.0.1, NTA 4.0.3, IVIM 1.10.0, VNQM 4.2